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The adult anatomy and histology of the anal glands of the Richardson ground-squirrel citellus richardsonii sabine.

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Un ivelsit y of C'olifomt in
The specialized integumentary glands of mammals have
been investigated in varying degrees of completeness by a
number of workers in the past. These glands, which are believed to be modified sudoriferous and sebaceous glands, may
occur in many places upon the exterior of the body, but perhaps the most important class of them (leaving out of consideration the mammary glands) comprises the glands which
are developed in the region of the anus. I n this region it is
common, if not invariable, to find the sebaceous and sweat
glands enlarged, and producing a secretion more o r less odoriferous. Frequently these glands are scattered diffusely upon
the wall of the anal canal or upon the skin of the perinaeum;
in many mammals, however, particularly among the orders
Carnivora and Rodentia, the glands may be aggregated into
masses of considerable size which arc provided with muscular
investments, storage vesicles, and ducts opening to the surface
on papillae. This degree of morphological complexity is associated with a corresponding elaboration of the physiological
functioning of the glands, the secretion being copious in
amount and containing special prodncts, usually of a highly
odoriferous character.
In 1874 Chatin published an extensive monograph on the
odoriferous glands of mammals, dealing with the anal and
perinaeal glands of the orders Carnivora and Rodentia. I n
JANUAltY, 1 9 2 6
the latter order he described tlie glands of Castor, Miis decnmanns, Ilnsyproeta, Atherurn, L e p s cuniciilus, arid Arctomys
marmottn. Tlie Carnirora, liowerer, have received most attcwtion i n respect of tliose glaiids. AIivart ('82) tlealt with
the t~xtei.nn1cliaracters of the glancls of Qeiictta tigrina and
Pocw~k ( '15) described the grosser morpliological f eatiires
o f the glantls of CIciietta par*tliiia mtl (Xvettictns civctta. The
lii,.rtology of the anal canal :ml its associated glands iii the
clog has hccn iiivestigatetl 1 ) ~ -1Iebi.ailt ( 'W), Zimmermaii
( 'O-l), ant1 ~ll~uleno~vitscli
( '07). ,\part from this work upoil
tlic (log, most of the papo?*sjust mentioned h a r e related ratlicr
I n o w t o the grosser aiiatomy of the glands tlian t o minute
histological struetiire, their purpose liaving bcmi mainly
taxonomic. TTliile Chatin presents the results of some histological study upon the glands of certain of the mammals
Iic tlr!scrilm, the only n.ork thc present writer has heen ahle
to discover treating exlianstively of I h e microscopic anatomy
of ;I mammalian anal gland is furnished by the papers on
tlie odoriferous glands of tlie sknnk, Mcphitis mephitica, first
by T. H. Aldricli, wlio tlcscrihes hiit does not fignre the histology of the glands iu a papw upon the clieniical natiire of
the secretion ( 'M), and by Blackmail ( '11).
In the case of the Rodcbntia, cornparatid:- little work seems
to have t)een done, at any rate 11-it11 which I am acquainted.
'I'he pcrinacwl sac of the guinea-pig was dcscrilxtl fully by
(irosz ( '04). Tlie only ~ v o r kI lmow of upon the squirrels
or closely related rodciits is tlic hricf account of the glands
of Arctomys marmotta (fam. Scinridae) by Chatin in his
lbaper of half a century ago. Cliatin figures three tubercles
opening into the mall of a poii~h,a t the bottom of which tlic
anus is situated, tlie arrangement being rerp similar to tlie
structures found in Citellus richardsonii. He does not, however, refer in any detail to the histology of the glands of
Arctomys, although he has dealt with this aspect at somewhat greater length in the case of several of the otlier mammals he describes. He refers, in the case of several of the
Carnivores, to tlie existence of two superposed muscular
zones ensheathing the glandular masses, tlie direction of
whose fibers is mutually perpendicular, and to the development of muscular septa penetrating between the portions of
the secretory tissue. He discusses the origin of these mnscles, referring to the theories of the earlier anatomists that
they might be ‘muscles ambiants,’ or derived from abdominal
muscles, but he states that lie arrives at no coiiclusions on his
own part. Blackmail, in investigating the musculature of the
anal glands of the skunk, refers t o the statements made else%--herethat there is a coiiiiection between the muscle sheath
and the tail which assists in tlie mechanical discharge of the
fluid when the tail is raised, but apparently the material at
his disposal did not permit of the fuller investigation of this
point. Blnckmaii describes, in the skunk, hantls ancl sheets
of unstriatcd muscle in the corinm of the gland vesicle which
he regards as a derivative of the muscularis mucosae of the
rectum, but puts forward no view as to the clerivation of the
striated constrictor sheath round the vesicle. I refer to the
muscles at this stage, lmxuse special attention has been paid
t o them in the present paper, and because they are features
of morphological importance in a stndy of these glands.
F o r the purposes of this paper the author has been favored
by an abuiidaiice of material which made possible observations upon tlie mechanical functioniiig of the papillae in the
living condition, and also the cutting of complete series of
sections across the gland masscs at various angles. The
ground-squirrel Citellus ricliardsonii’ is the commoii burrowing mammal of the prairies of North America and was readily available on the campus of the UniversitJ- of Saskatcliewan, where a portion of this work was clone. The animal can
be obtained by trapping, ancl, if not too seriously injured in
the trap, will recover in captivity. It requires but little observation to note the conspicuous papillae of the anal glands,
which are protruded ~ 7 h e nthe animal .is alarmed. The
Coinmoiily known as the gopher, though the name prairie goplicr is more
correct, since the true or pocket gopher, Geomgs bursarius, beloiigs to different
family of rodents, thc Geomyidne.
author’s interest in this subject, indeed, was aroused in this
I n order to iiivestigate the structure of these organs, dissections ~vc1-cperformed to elucidate tlieir grosser features,
:tiid then tlie glmds, together wit11 the anal canal aiid a portion of the perinaeum, were removed and fixed in Bonin or
Zcnker. It was found also that tlie glands from specimens
preserved in formaliii gave quite good results from tlie histologicd point of view. Four sets of glands were embedded
and cut into serial sections at tliflcrerit planes. In all some
900 sectioiis were studied, and the relationships of the differeiit tissues were elucidated by tracing them out in the series.
By this mcans a complexity of structure was revealed greater
than that indicated in previous accounts of mammalian anal
glands, and it h a s been possihlc to establish definitely the
~*clatioiisliipsof tlici musclo slieatlis ( f o r this ttiiimal a t all
Chatin’s account appears to reveal two clistiiict tciidciicies
along which the evolution of the aggregated gland masses in
mammals lias proceeded. On one hand, the aggregation has
takeii place upon the pcrinaeiim, such perinaeal glands, some
distance au-ap from tlie anus, producing a powerfnl but not
foetid odor; and, on the other liaiid, the concentration has led
to complex glands upon the wall of tlic anal canal, or anal
glands, -cs-liichare usually hidden wlien the anus is contracted
and whose secretioii is often highly foetid. I n many mammals, notably tlie civets and the beaver, both kinds of complex glaiids occur together. A further class of glands is
worth>- of mention, namely, tlie prepntial glands found in
the rat and other mammals, which are to be assigned to a
different category, since they appear to be dcriwtl from accessory rcproductivc g1:~nds.
TVlien largc aiial glands arc tle\-elopecl, tlieir iiumber is
usua11)- t i n ) (right and left of the anal axis). In Arctomxs
tlic iiiimhcr is three, oiie of wliicli is median, aiicl this obtains
for Citellus, too, though sufficient data are not to hand to
say whether the possession of three glands is characteristic
of the Sciuridae.
The three gland masses in Citellus are enclosed in a common investmeiit of areolar tissue and striated muscle, and
they open in the retracted state by three large apertures upon
the anal mall (fig.3). Chatin, in the case of Arctomys, refers
t o the glands as opening into a pouch, at the bottom of which
the anus is situated. The designation of a special pouch appears to be arbitrary in the case of Citellus, or at any rate
if such a pouch can be said to he marked off, it is merely a
portion of the anal caiiwl. The three glands open upon the
anal wall or, if preferred, the region of transition between
anal membrane and skin. As will be shown later, a study of
the musculature of the glands suggests that thcj- are embedded within tlie sphincter externus of the anus, and there
appears to be little reason for designating this portion of
the anal canal by a special name.
Normally, the openings of the glands are conccaled within
the anal orifice, but the animal has the power, by voluntary
action, of everting the channels which then protrude from the
relaxed aims as three stout diverging papillae of a reddish2
color (figs. 1,2). As far as my observations upon the living
animals show, the papillae are protruded when the animal
is irritated or alarmed. When one approaches tlie trap, the
captured animal will deliberately display its anal region, protruding the papillae spasmodically in a manner which suggests that the:- may h a m a sematic function. The animal
turns upon its hack, uttering sharp cries, and protruding the
papillae, which give it a somewhat startling appearance and
might conceivably cause a dog to hesitate to attack it. No
secretion is apparently discharged under such circumstances,
at any rate not forcibly, and, since the secretion is practically
odorless and non-acrid, it is not easy to understand why the
animal should make a display of the papillae when attacked.
The reddish color of the papillae is merely due to the abundance of vascular
dermal papilktc of the corium of their integumciitltary lining, not to pigmentation.
r i
1 lie wariiiiig function is of course merely a suggestion. !L‘hat
t h e glands play some part in the defense of the aiiimnl is
suggested by the fact that the animal will frequently endeavor
to i.cnch the hand with its anal region, and the clisc.harge of
sccretion can he promoted by touching the protruded papillae
witli the end of a stick or other hlunt object. The secretion
is a thick c l o u c l ~fluid, of a cream or pale hrown color, c o w
taining in suspension the keratinized remains of clesquamatcd
tyitlielial cells and protlncts of nuclear degeneration.
I f R freslilj- killed animal he subjected to pressure in the
aldominal region, the anal ~ m l is
l caused to stretch and tlie
openings of tlie introverted chaiiiwls can he seen within the
anal orifice (fig. 3). The opcnings are tlircw in number, appcaring as ratiially disposed slits, with somewhat tumid lips,
as figured by Chatin for Arctomys. They belong to the vent r d half of tlic anal wall; one of them is median and vcntral,
and the other two right and left, situated nearly half-way up
the anal x - d . The channels of the glands, when everted as
papillae, arc thus situated on the side of the ma1 wall toward
the genital aperture. If an incision be made through the skin
SO as to surroiintl the anus ‘and tlie peririaeum up ‘to the urogenital aperture (in the male the testes are retracted except
at the breeding season, 8 0 that tlic operation is simplified by
the absence of the scrotum), and the portion of the skin tlius
separated from the rest is raised and examined from the
inside, n hulbous mass iiivestccl l y coiiiiectivc tissue and fat
can be seen in the angle between the lower portion of the
reetum and tlie shin of the perinaenm. This mass is about
the size of a large pea, and, 1s’hen the loose coniiective tissue
is tlissccted away, is seen to consist of three snbclivisions,
closcly apposed and united by a firmer slicath of connective
tissne and mnscle (fig. 4). Each of these three subdivisions
is an independent mass of glandular alveoli, comprising, as
x-ill be shown presently, two distinct kincis of glandular elements, surrounded by its om11 investing layers and provided
with its own evertible channel. One of the glandular masses
is median and rentral and the other two are closelp apposed
to it on each side. The three glands are enclosed by a common sheath of loose areolar tissue, which is continuous with
the paniiiculiis adiposus of the adjacent skin. It was this layer
which was nieiitionecl above as requiring to be dissected
away to reveal the triple layer of the wliole glandular mass.
The glands are seen now to be surrounded by a sheath of
striated muscle. A cross-section shows that, this sheath is
prolonged inward between them in the form of two septa
(fig. 7, 9). Each gland consists of, a ) a n outer mass of secreting lobules ( 2 ) lying immediately below the constrictor
slieatli of muscle, and loosely surromicling b ) a considerably
larger mass of lobules of a different kind of glandular tissue
(.lo), opening into the base of the everlihle channel. By the
coritractioii of the muscle sheath aiicl its septa, the masses are
compressed and the channels are everted as papillae.
The three glands are invested beneath the skin by a mass
of loose coiiiiective tissue, already refrrrcd to as a portion
of the panniculus adiposus pushed inward by the develop ment of the glands. This appears vesicular in sections
prepared in the usual way, the fat having been dissolved
out. Within the panniculus adiposus the glands are surrouiidetl by a firm investing sheath of striated muscle; this
muscle layer consists of numerous flattened fasciculi whose
arrangement reveals that the layer is donble. The outermost
portion constitutes a common shcalli f o r the three glands,
which themselves are surrounded individually by coats of
striated muscle (fig. 7, 6 , ~ ) .The outer coat is common to the
three glands and its fasciculi ruii at varying degrees of inclination around the whole mass, forming. the maiii constrictor
muscle. This sheath is complete everywhere around the fundus portion of the glands and is continued toward the surface
of the skin on the side away from the anal canal. Between
the glandular masses and the anal canal it is very thick (figs.
8, 12), becoming continuous with the sphincter ani externus.
If the panniculus adiposus is clissectcd away from the angle
hct ween glands and rectum, and the glands are then stretchecl
away from the rectum by their fumiuses, the junction between
the cwmmon constrictor muscle and the sphincter ani externus
can be seen as three thickened areas, one region of the tliickcning being opposite each fundns (fig. 5 ) . The striated musel(. sheath is lackiiig from the extreme corner between the
anal canal and the secretion channels formed by the intro\-crtetl papillae. The common constrictor is covered on its
outer and iiiiier faces by a laver of areolar tissue. This constitutes the epimysium of the mnscle and merges on the outer
sitlc with the panniculus adiposus. On the iiiner side it merges
with the cpimysium of tlic imperfectly developed individual
constrictor sheaths, in places passing between their scattered
fasciculi t o become continuous with tlie framework of the
areolar tissue which supports the glandular alveoli (fig. 6).
The muscle sheaths of the individual glands consist, like the
common sheath, of striated muscle grouped into fasciculi running at various angles to one another. These three inner
sheaths, however, are comparatively poorly developed and in
many places incomplete. The demarcation between the inner
sheaths and the common outer sheath is often represented in
section by a distinct space containing connective tissue formed
hp the adjacent epimysia. I n other places the fasciculi of
both sheaths approximate so closely that the distinction between the two sheaths is lost. If one of the fasciculi in the
inncr sheath of either lateral gland be compared with the immediately superposed fasciculiis of the common sheath, it is
generally to be observed that the directions in which the two
fasciculi run, as indicated by the shape of the cut ends of the
muscle fibers, are inclined at an angle of about 90". I n the
case of the median gland the fibers of the inner sheath and the
common sheath run nearly parallel (fig. 7 ) . Since the inner
slieaths circle the glaiids individually, the median gland is
separated from the outer glands by a septum of muscular
tissue formed by the apposition of the inner sheath of the
mctliaii gland with the inner sheaths of the lateral glands
(fig.7, 9). The double origin of this septum is to be seen in
section wlierc the septnm meets the periphery of the glaiid
mass. The outer glands are roughly of a hemisplierical shape
(fig. 7 ) , closely apposetl to the median gland which is of a
short subcylindrical form. Thus the separating mnscular
septa are roughly cireular ant1 flat. Round the periphery of
the circular septum the separation of the two iiiiier sheaths
forming ’the double septum from each other and from the
common outer sheath is marked by a triradiate mass of arcolar tissue derived from the meeting of the three cpimysia
(fig. 7, 5 ) . I n the septum, which itself possesses little connective tissue, the fasciculi derived from both sheaths ruii
parallel, and the double character of the septum is often lost.
The dividing strip of areolar tissue, represcnting the epimysia
of the two coats forming the septum, 1)reaks up into diverging
fibers which spread as epimysial partitions among the iiidividual fibers irrespective of which sheath they belong to, so
that in the central zone of the scptnm complete merging of
the two sheaths may be coiisiclcred to have taken place. I n
one of the sectioned specimens, however, the division of the
septum was apparent across its mholc extent.
The fact, previously poiii
out, that the striated muscle
associated with the gland masses is coiitinuous with the
sphincter mi exteriiiis, shows clearly its derivation. The
glands arc to be regardecl as iiivaginatioiis of tlie anal wall
carryiiig the sphincter liefore them. From the sphincter 1)ecame developed their iiirestmeiits of voluntary constrictor
muscle. With reference to tlie areolar tissue forming the
epi-, peri-, and enclomj-sial slicatlis of the fasciculi and muscle
fibers, it may be pointed out that this mid the areolar tjssue
forming the framework supporting the glandular alveoli are
both identical in structure and continnous with the corium of
the periiiaeum, and therefore presumably derivatives of it.
Giant muscle fibers were f omit1 occasioiiallp in the wnstrictor coats, usually ill the angle between the glands and
the rectum.
rlllle clversioii of tlie cliaiinels and the discharge of stored
sec.wtion a r e effected by tlie coiitractioii of the striated constrictor coats. Relaxation of the anal orifice occurs to allow
the j~apillaeto protrude, whicli implies that tlie end of the
sphiiicter proper is relasocl while what is equivalent to a
1)ortioii of it, namely, the miisci~larcoats o f the glands, is
cwiitr:ictetl simnltaiieously. ‘l’he cflect of the pressu1.e prot l i i c ~ ~1)y
l the muscular contraction upon the plastic alveolar
m a s s witliiii is t o bring about evagiriation of the normull:iiitroverted papillae. Siiicc tlie triple gland mass is of an
o v a l shape, the development of mnscnlar septa. separating tlie
glaiids is a provision to insure tlie equalization o l pressure
upon the glaiidular tissue ; other-v;ise the contraction of a
purcly periplieid muscle sheath would tciitl to press the mass
iiito a spherical shape, losing some of the contractile effort
iii so doing, before the papillae w e i ~everted. Each of the
glands is compressed by its indivitlnal sheath, and tlie three
glands al-c compi.essct1 I)?-the commoii outer sheath. Since
t l i v glards arc tlisposecl side 1):- side, the combined effect is
t o ~)rocluceclivaricatioii of the protruded papillae (fig. 2 ) .
The papillae tliemse1.i-es a r e deroid of intrinsic muscles, arid
they Iiave iio power of mo\-emeiit, as far as conld he obscrved,
other tliaii that of protrusion aiid witlidrawal. In this respect
they dift’er from the skunlc, where tlie papilla can he directed
in position so as to discharge the fluid in a desired direction.
‘l’lic gopher makes a tielibcrate display of the papillae, and
it is to be observed that tlieir protrusion is of a spasmodic
iiatiue. They a r e everted sliarplq- a i d suddenly, relaxation
o f the coilstrictor mnscles occurring almost immediately. The
papillae are then introverted more slowly and disappear
n-ithiii tlic aiius, the orifice of which closes ovcr them. The
hotly of the protruded papilla is filled hy the glaritlular tissue,
\vIiose tlis;I)lac.ement lry the coilstrictor cl-eates the papillit.
It is evident that introversion of tlic papillae must be
effected by definite retractor muscles, for mere relaxation of
the constrictor coat would not be adequate to bring about
their withdrawal. The fact that the papillae were withdrawn
more slowly than they are protruded, moreover, seemed to
indicate that the retraction was effected by unstriatcd fibers.
Clliatin, while referring to the occurrence of ‘muscle lisse’ in
tlie anal glands, does not discuss the question of the retraction of the papillae when tlic latter are introvertible, as in
the marmot, 1101’ docs Blackmar, in reference to tlie skunk.
Inched, thc possibility o r even the need of muscle acting antagonistically to the constrictor-protractor coat might readily
be overlooked. On finding that thc: voluntary constrictor muscles of the glaiids were derived from tlie external sphincter,
I thouglit it not unlikely that the internal (involuntary)
sphiiictcr aiii might furnish the retractor muscles of the
papillae. Search was therefore made through the series of
sections to discover the retractor muscles and establish their
relationships. As a result of this, it is possible to affirm that
the retraction of the papillae is effected by unstriated fibers
derived not from the sphincter iiiternus as I had expected,
but from the longitudinal muscle coat of the rectum, wliicli, in
Citellus, extends down between the sphincter externus and
the sphincter internus. (In most mammals the longitudinal
muscle layer of the large intestine does not extend into the
\vall of the anal carial, though it would be interesting to esamine those that possessed protrusihlc anal papillae, to see
if a similar arrangement did not obtaiii.) In the skunk, Blackman refers to bands and slicets of unstriated muscle in the
pars reticularis of the corium of the vcsicle, which are derivatives of the muscularis mucosae. He does not, however, refer
to the muscle layer proper of the rectum (which is distinct
from the muscularis mucosae), nor to tlie relatioiisliip of the
strands he specifies to tlie niccliaiiism of retraction of the
papillae, if any relationship exists.
The fibors of tlie longitudiiial coat of the rectum (fig. 10, X )
are collected hetween tlie t x o spliiiicters into a number of
fasciculi of different sizes which are inserted at their lower
ends into somc bandles of white films which serve as the
retractor ligaments of the glands. These retractor ligaments
are three in iiiimber, oiie for eacli glaiitl, anti the central one
supplying the median glaiiti is the largest and the most tlefinite
in structure. This median retractor ligament is in the form
of a promiiieiit band of white parallel fillers (fig. 10, 3 ) runiiirig in tlicl mecliaii plaiic from a group of the fasciculi of
iuistriattd muscle lying about the midventral line of the mall
of the anal canal. I n this gronp (2)the median fasciculus is
distinctly larger than the others n.hicli lie to riglit aiid Ieft of
i t , all attached to the frayed end of the median ligament.
It will be remcmbcred from the preceding account that tlie
striated coilstrictor coat is exwptioiiallj- thick i l l the angle
hctwecn glands and aria1 cmial ; that is, ivhere the musc~ular
coat takes origin from the sphincter aiii extcrnus. Across this
tliickencd regioii the mediaii ligament runs in .the median
plane, sliarply interrnptiiig the striated fihers, whidi rim at
riglit angles to it. Their sarcolc?mmas are inserted upon the
ligament, nhich runs back so as to bisect the sphincter cxteriius for some distance, till it joiiis tlic plaiii muscle of the
longituclinal or middle coat. In other words, the sphincter
externus aiid the constrictor sheath of tlic glands are bisected
iii the midplaiic) hy the ligament, tlicir striated fillers heing
actnally inserted iipoii it. ‘I’lie meclian ligament extends from
tlie im-oluntary fascicuii through the lo\wr portion of the
sphincter ext eriiiis a i d tlicii sciicls an offslioot t owarc1 tllc
angle between tlie median glaiid nncl the aiial canal. The main
portion of it continues roiiiiil the fundus of tlie median gland
(fig. 11, lig.) and mcrges into tho arcolnr reticuliim which
iiiwsts the alveoli of tlic gland. l’his ligameiit tliirs lias
somewhat tlie same relatioil to the gland that the liaiid would
hare to an orange that was held in the angle between tlie
t l i i i r n b a i d the rest of tlic liand, tlie thixmb and fingers hciiig
ontstretc4ied in one plane. Since the ligament merges into
the reticulum of the gland, the tension it exerts is distributed
to the ~vliolcglandular tissue and to the base of the channel
which becomes the summit of tlie everted papilla. Hence
when the retractor muscles contract tlie papilla is introverted.
In tlie case of the two lateral glands, tlic retractor ligaments arc not so highly developed, heing in the form of diffuse
bundles of white fibrous tissue (not organized into a plane
sheet like the median ligament) running, in tlie retracted
glands, in a roughly curved direction on each side of the axis
of the gland mass, and a t a lower level than the median retractor ligament (fig. 12, 7, 7 ) . They are continuous proximally with fasciculi of plain muscle situated more laterally
in the wall of the lower portion of the rectum which, like the
retractor muscles of the median gland, belong to the longitudinal coat. Distally, the lateral retractor ligaments spread
out laterally to connect diffusely with the supporting reticulum of the lateral glands. The lateral retractors extend
nearer to the mouths of the inverted channels than does the
median ligament, so that in the photograph (fig. 12) only the
lateral retractor ligaments are seen a t the particular level
of the section. In this region also, which is close to the opening of the median gland upon the anal wall, the constrictor
coat is absent except a t tlie sides where tlie thick masses at
the junctions between sphincter and constrictor are seen, the
striated muscle not extending into tlie extreme angle between
glands and anal canal. The lateral retractor ligaments interrupt the constrictor coats of the lateral glands, whose fibers
are inserted upon them just as the fibers were inserted upoil
the median retractor at a level nearer the fundus of the median
gland, though in thc case of the lateral ligaments the interruption to the muscle substance is not of so rigid a nature.
The insertion of the striated fibers which serve for the protrusion of the papillae upon the ligaments ~ l i i c hserve for
their retraction seems anomalous at first sight. It must, however, he borne in mind that the median ligament runs at right
angles to tlic striated fibers whosc opposed contraction prodnccs no movcmeiit in it, while the involuntary fibers rhich
pull tlie ligament are colliiicau with it. Tlie ligament constitutes merely an interruption in tlie contrictor muscle of 110
nicrliaiiical significance. In the case of the lateral ligaments,
some striated muscle is iiiserted upon their lateral sides. Very
little muscle is inscrtccl upon the medial sides of tlic lateral
ligaments ; oil this side each ligament merges into a mass of
arcolar tissue in the top portion of tlie angle between median
clianncl arid the sphincter aiii intcrnus (the sphincter esteriiiis, a s explained, being absent from the extreme corner).
This intervening tissue is equiralent to a supporting conncction between the lateral ligaments against the coiitractioii of
the striated fibers which arc inserted upon their lateral sides.
THE STIi1’(’TTTRE Oh’ ‘I’IIE IiVrl‘i<Ol’b~RT~~D
~:acliof the three glaiicls discharges its secretion through
i i i i aperture tit tlic extremity of tlie evei*teclpapilla. The latter.
is abut 8 mm. iii leiigtli and 3 mm. thick, cylindrical or
slightly barrel-shped. Ordiisarilp, the papilla is introverted,
f ormiiig a capacious cliannr~lleading from tlie glandular mass
to the amil wall (fig. G ) . The term ‘chaniiel’ is preferred to
‘duct ’ for several reasoils. Altliongli tlic introverted papilla
is equivalent to ail inr~aginationof the cctoderm (of the anal
wall), such an involution caiinot lw compared to the type of
i~ivagiiiatioiirepresented 1))- tlic duct of a sweat or a sehaceous
glaiic3. In tlie first place, the iistrovert is riot pwmanent, siiicck
it can he turiiecl inside ont ; a r i d iii tlie g l a d s , j u d mentioiled
t h e irivaghitition is a doiviigi~)ivthof the retc I ~ I I ~ O ~while.
I I ~ ,
in tlici case of tlic clianriels of the anal glaiitls the whole skin
is I)odily iiivdvtvl, mesoderrti as w-cll t i s ectoderm. The ti*uc
(iuc‘ts, moreover, as distingiiishctl by their histological structurp and their relationship to the alveoli, are not cxtrovertible, aiid they represent true iiivagiiiatioiis of tlie base of the
(*liannel,which itself is to be regarded as a pocket of the skin.
If tlic channel be examined in section (figs. 6, 9), it will
be observctl that its wall exhibits thcb structure of mammalian
skill devoid of hairs a i d sweat gllaids. Adjacent to tlie lnmeii
of the clianiicl is fi stratum (v)ixeimi of csccptioiial tliickiicw
which presents an irregularly laminated appearance, owing
to the presence of many partly dissociated layers of the keratinized remains of the epithelial cells. It will be understood
that when the channel is everted, the stratum corneum borclering the lumen of tlic cliannel in the retracted state becomes
the outer layer of the protruding papilla. Hence the thickness of the lining of the channel, which would be unusual
were the channel always in a state of involution, can be accounted for, since the papilla will need a well-developed protective surface. It is to be noted, however, that the stratum
corneum of the channel is considerably thicker than in the
adjacent anal wall or even than iii the normal skin. This
point, in my opinion, is worthy of note, f o r in the anal glands
of the gopher we fincl a remarkably high production of keratin
in the form of shed-off keratinized cells. This tendency is
well illustrated when we proceed to study the parts of the
gland immediately connected with the channel.
At the base of the channel the stratum corneum of the wall
frays out in a very noticeable manner (fig. 9 ) and the dissociated laminae form ail irregular spongy reticulum of highly
lreratinized material. Into this spongy mass open many ducts
from a series of lobules (fig. 6, 13) which constitute the bulk
of the glandular mass. The number of these lobules is about
forty f o r each gland, and each lobule contains seventy or
eighty saccular recesses or alveoli densely filled with epithelial cells. The central portions of these alveoli form a
racuolated spongy reticulum (fig. 1 3 ) continuous with the
l , serving to lodge
reticulum at the base of the c h ~ n i i ~and
the more fluid secretion of another series of glandular clcments outside tlic lobules just described. The channel often
contains a considerable amount of the desquamated seeretion
mass (fig. 6, 3 ) which, iiear the mouth, is often mixed witli
sand grains a i d other debris from the outside (1). It will
be borne in mind that what is referred to as the month of
tlic chaiincl ~vlieiillic gland is retracted forms the circular
base of the papilla when eversioii occurs, and the 1)ase of tlie
channel into wliicli tlie ducts opcii come8 t o the top. Thus,
any matter lying in tlic channel will be discharged when eversion takes place, aiid the spongy reticulum at the base of the
cliannel will be brought t o the surface. The protrusion of the
papillae is not accompanied by discharge of secretion on every
occasion. Frequently they are protruded by wily of display
without any expulsion of secretion. Presumably additional
muscular contraction may be necessary to discharge the secretion from the spongy mass after the papillae are protruded,
o r it may be that the secretory activity is rariable, the fluid
secretion not always being present in sufficient amount. Some
observations showed that it merely required contact with a
foreign object to arouse discharge; at other times tlic creamy
fluid was to be found upon the fur of the animal in the anal
region when unprovoked by any external irritation.
TJnderlying the stratum corneum of the channel wall is a
stratum granulosum of two o r three cells in thickness (fig.
9, 6 ) . I n some places the eleiclin granules are difficult to
detect. They are mostly strongly developed where the stratum
cornenm is tliickest. Tlie stratum lucidurn of the normal Sliin,
a s far as can be asccrtninetl, is lacking from the epidermis of'
t h e papilla. Ti1 a few placcs a slight transparency could be
dctccted in the lower layers of the stratum corneum, but this
was indefinite both in extent and thickness aiid could not be
clefinitel:- identified with a straturn lucidurn. Within the rete
mucosum iiumerous dermal papillae (fig. G , 1 2 ) are t o bc seen.
'l'hq project into the epidermis obliquel?-, and in section they
appcar freqneiitly as detachctl clnmps of cells. They cntcr
tlic lower layer of tlic rete mucosum hy narrow necks and
tlieii expand. No tactile corpwcles could he found in t l i ~ ~ r n ,
though they a r c x-er5- vascular. Their great niimber connotes a large blood supply to the wall of the chaiinel and hence
high nutritive requirements, cloubtless associated with the
imusixally lieavy formation of stratum corneum. Indeed, the
increase in tlic iiumbev of dermal papillae is ver;v markcti at
the entrance to the chaniiel, if the skill is followed in the
wctioii along the anal wall and into the cliannel (fig. 8). The
1~roiioiu1ceclthickening of the stratum corneum also hegins
in the same place.
At the lower end of the channel, concomitantly with the
fraying out of the stratum corneum, the cells of the rete
mucosum become enlarged (fig. 9) by both cytoplasmic and
nuclear growth. Cell divisioii in this region is not marked.
There is thus produced at the base of the channel a region of
swelling of the rete mucosum, whose cells are desquamatecl
off and undergo immediate disintegration after keratinieation
without passing through the normal compact stage of a
stratum corneuni. This result may be due to mechanical
breaking of the stratum at this region during eversion, but
more likely it is a manifestation of the transition of the epidermis into the sacculated gland masses now to be described,
Reference has already been made to the existence of two
distinct types of glandular tissue forming the mass between
the base of the channel and the muscular investing coat. The
first type of gland elements to be encountered on proceeding
iiivard comprises a dense mass of lobules immediately surrounding the base of the channel and occupying the greater
part of the whole gland. Their ducts are continuous with
the rete mucosum of the channel wall. Active desquamation
of epitliclial cells takes place in their alveoli and ducts, the
desquamated cells being filled with particles of fatty material
and undergoing disintegration to form a reticular mass which
becomes highly vacuolated and drawn into irregular strands,
The vacuolation becomes more and more pronounced as the
secretion mass passes on toward the base of the channel.
Figure 15 is a high-power photograph of the alveoli of these
glandular elements, to show how they are filled with epithelial
cells, and it will be noticed at once that they resemble very
closely sebaceous glands unassociated with hairs. Hairless
sebaceous glands are well known ; also sebaceous glands associated with a rudimentary follicle (Sappey). I n one instance
a reduced and imperfect hair follicle occurred buried in the
glandular mass, affording definite proof of the relation of
the lobules to sebaceous glands, and suggesting that they
twloiig to S a p p y ' s sccoiid category. Cliatiii regards all the
;ilia1 a i l ( 1 pcririeal glands lie examined a s derived from seba(w)iis glands. B. Rosenstadt has shown tliat a part of the
c d l snbstance in sebaceous glaiids undergoes keratinizatioiin fact ~ d i i c l is
i amply illnstrated here. The cXesquamated cpitlielial cells are seen t o be liiglily keratiiiized, especially as
t licy pass progressively toward tlie mouths of the d ~ e o l and
down the ducts. I t seems possible, therefore, that the aria1
glands in ('itellus may function f o r the disposal of superfluoils kei-atiii i n 11 maiiner comparable to tlie slieddiiig of hairs
a i d antlers in other mammals. Tlie production and elimiiiatioii of keratiii mnst be relatively enormoils in tliese glands,
aiicl it is to be noted tliat we find the same teiideiicy illustrated
in tlie very tliicl; stratnm coriieiim of the papillae, which can
Iiartlly hr iiecdctl for nicro protection. I Iiave not snfficiciit
iiiformation t o malie a compai~isoiiwith otliei. mammals IJOSscssiiig aiial glands with regard to tliis suggestion of a
keratin-climinatiii~function. 1 am iiiiaware of tlie point's
Iinviiig hccii raised before.
W e 1 1 0 pass
on i o stntly tlic secoiicl tFpe of glaiidular elem d s presciit in tlic aiial gluntls. Tlicse consist of l o l d e s
smaller in size aiicl iiumber tliaii tlic first (fig. 6, 7). They
itre compressed between tlic latter and the muscular capsule,
heiiig slightly separated from both by arcolnr cwriiiectiw tiss u e wliicli may be coiitleiisetl iiito dense strands in places.
E~;wliof tliese outer-lying 1ol)ules is of the compouiitl racemose
type terminating i i i saccular alveoli lined by columiiar or
cubical cpitliclium surrouncled 13)- a hasemcnt mem1)raiie (fig.
16). The iiuclei of the cells are situated in the h s a l portioii
of Ilie cell. The free extremities of thc cells are oftcii clra\vii
out into pear- OF club-shaped proc'csses, aiitl tliis appears to
he a prelimiiiary to the sliedtling of the cell into the lumen
of tlie alveolus. The lumen is distinctly open, in sharp coiltrast to tlic first iypc of alveoli; within it arc to be seeii
many of the lining cells set free. l ' h c ~ eshed cells uiidcrgo
cytolytic aiid ctcgeiierative chaiiges preseiitlr to be referred
to, aiicl often become aggliitinated into masses oeciipyiiig the
lumen. Although tlie bodily destruction of gland eells as a
concomitant of secrctioii is coilsidered to be rare, it is generally admitted in connection with the sebaceous glands. We
have, indeed, already described it in connection with the first
type of glaiiclular elements. There is reason, therefore, to
regard the secoiicl type of elements as sebaceous glaiids like
the first, though, as will be seen from the photographs and
figures, they differ markedly in possessiiig open Inmiiia ant1
in the character of tlie lining cells. The latter resemblc very
closely the secreting epitliclium of a mammary gland, although
the latter is not usually regarded as derived from sehaceous
glaiids. If figure 16 is compared with tlic photograph of a
section of the mammary gland gircn on page 287 of Schaeffer 's Kssentials of R i stolog-, 1l t h edition, this resemblance
will he very ol)vious. Some of the cells, moreover, exliihit a
fraying out of their free eiicls, which Blackmail stwtes is kno.c\rn
to O C C I I ~in tlic mammm-y glaiid.
That tlie glaiicls uiitlc~clescriplioii, liowevcr, are sebaceous
glands, like the first type, seems to be proved coiicliisive1~-by
the discovery of a rudimentary hair follicle associated Ivith
one of them (just as Iiappened in tlie case of the first type
also). The epithelial cells a r e variable iii different glands
o r in differelit nlvcoli in tlie samc gland. Doubtless, the clifferences are t o 1)c assigiied to different states of secretory
activity, for tliesc alveoli a r e the oiies in which tlie more
fluid portion of the secretion is formed. 111 most eases the
cells are as clesciibcd abovc, with hroad loosc extremities,
but in some alveoli tlicy mere fomicl to be very liiglily colnmnar, their halves to~7arclthcl liimcii bcing clear and liomogeneous and abutting closely upon the rctluced lnmeii so that
no irregular spaces lay lietween the ontei* portioiis of the
cells as happelis ~ 1 1 ~ tlicy
~ 1 1 asslime llie club-shape. KO polymorph iiuclci were ciicouiitered comparaldo to what Blackman found in the skunk; but of course the comparisoii with
a different ortlcr of mammals is rather a tlislaiit oiic to make.:$
The frequeiit e o n q ~ ~ r i s o nwith
the skunk made in this paper arise out of
the fcict t h t H l a c ~ k m 'Y: ~ papw
is flic onI;v work known t o me wliic*h deals in
111 tlic slilllili, agaiii, 110 hlie~ltliiigof cells into tlie lumc~iiis
The assiinipt ion of tlie irregular sliapes of the epithelial
c.ells is to be regarclecl iis ii preliminary to slietldiiig, for in
sncli alveoli the lumeri alwa~-scontains a mass of shed cells,
while other alveoli possessiiig a regular wall l i a n a clear open
lrinicii. T h ( ~open o r half-opcm cliaracter of the lumen, as
compared t o the first-type lumen, iiidicates that it contaiiis a
coiisi(1erable amount of flnitl clerivcd from the epithelium.
Tlie lohides of the s;ecwici type possess tlucts of considernhle
length, and fairly thin (fig. i , 3 ) . There is a sharp transition
iii tlie epithelium at the junction between duct and alveolus.
‘l11iewall of the duct is cwmposetl of several layers of compact
stratified cells, taking no part in the secretor>- activity or in
clesquamatioii (fig. 1 G ) . Tlie ducts often divide sliai*ply into
two to coiinect with adjaccxiit lolniles, and braiicli williiii tlie indir-idual lobes to serve the alveoli. They run in the coiiiiectiwtissne stroma between the alreoli and tlie strands separating
tlie lobules of the first type from those of tlie secoiid type,
ant1 theii ruii hetween the lobules of the first type (figs. 15, 19),
t o ope11 directly into the Imse of the c2ianiiel (or the summit of
the papilla), along with the ducts of the first type. The
secoiid-type ducts are very different in character from the
first typc. They are longer and iiarrowcr and have a definitely spwialized wall, while the latter are little more than
the mouths of tlie cleiisclp filled saecules. I n their course
throngh the mass of first-type lohules tlie scconcl-type ducts
are invested by sheatlis of connective tissue (fig.15). Occasionally tliese ducts are disteiided by dense agglutiiiated
rnasscs of material (fig. 14, 4 ) prohably derived from the
secretion products of tlieir alveoli, though the origin of these
tlisteiisioii masses lias iiot heeii ascertained.
The spoiigy rcticular mass filling the months of the firsttype alveoli and the base of the channel apparently serves as
clet:iil with the Iiistology of ail :mil gland. I t should be understood, moreover,
tlmt HI:ickm:r~~t l r y i v e s the odoiifrrous glands of the skunk fioin swt:ut, 110t
srb:ireous gl:intls, for reasons \\hicli will Lc :ipparent if his paper be consulted.
an absorhiit matrix to hold the more fluid secretion of the
seconcl-type glandular elements. In Chatin’s account of the
glaiids lie studied there is no mention of two types of glandular elements.
I n two out of the four sets of glaiids sectioned there was
found a single small gland identical in histological character
with a detached second-type lobule situated outside the common muscular sheath on the side of the gland mass away
from the anal canal (fig. 8, lo). The duct ( 2 3 ) was single and
w r y long, filled TF-ith a vacuolated secretion mass as described
f o r the second-type lobules (p. 20, fig. 14, 4) and it opened
upon the perinaeum close to the anal orifice, in one case into a
hair follicle. Here again the relationship to sebaceous glands
is well illustrated by wliat appears to he an abnormally situated second-type lobule (outside the muscle sheath instead of
As has already been explained, the cells lining the secondtype alveoli exhibit in most places club-shaped enlargements
of their free extremities. The nucleus of the cell is normally
situated at the base of the cell next t o the basement membrane, but when the enlargement begins the nucleus migrates
outward into the enlarged extremity. Sometimes (fig. 17)
the enlargement of the cell is general. The interpretation
of this is that the cell has room t o enlarge sideways through
a contiguous cell having moved away. During enlargement
the cytoplasm becomes pale and the nucleus invariably moves
away from the basement membrane. Cytolysis is taking place
in the cell, and it can be seen in A how the nucleus is partly
filled with fluid, the result of chromatolysis, and how the
remaining cliromatin has broken into two masses. The fluid
nature of the cell is evinced by its globular shape. The cell
has already moved away from the basement membrane, its
place being taken by the eiicroaclimeiit of the two adjacent
cells, rliich by lateral enlargement have met beneath the cell
that is being shed. When the cells are finally shed, the nucleus ofteii becomes very small and opaque. The nuclear
remains of tlie corpuscle oftcii take on a crescentic shape
( C , I), E ) , at one end of the origiiial nuclear cavity, the remili iitler being occupied by fluid. The nuclear remains are
later protruded from the cell w1iolc (11) or iil fragments (F).
In P it is to be seen that the cytoplasm of the shed corpuscle
has 1)ecomcI filled with large mcnolcs of fluid.
E’reqiieiitly ciicystmeiit of the clesqnrimatetl cells occurs (N),
111e i i t t c l i i o r being fillctl almost eiitircly with fluid cwaept for
t l i ~tiiwlear remains, aiitl it is to be o1)scrvccl that the iiuclcar
rncmlnxne a s well as the cell mem1)ranie is keratinizcd. Thcse
od cwrpusclc~spersist ;is iidepeiicleiit Imlics among tlic
tlt’iisc aggliitiiiutetl mass ckrivetl from the other shed cells
d i k h may not have uiitlcrgoiie an itleiitical form of trailsfoi*mzltion. Tlic former are to 1)e found even in the i*cttiriilurn
of tlic first-type alveoli and in tlie clianiiel (fig. 13, :I). T’lir,
cwcystetl corpuscles may cveii uiiclergo cell dil-isioii. The
process, f i o w ~ ~ ~ tappcars
to l-tc tlcgcncrativc, for the resulting iinclei arc’ fragmeiitetl aid their cytoplasm is uiitluly fluid
( f i g 18). 111 figure 18 it is to be observed that an eiicptccl
corpuscle has become embetltled in the epitlieliiim of a firsttype duct. Thc nuclei of tlic ‘secoii(1wy’ corpuscles that do
not iiiidergo eiicystmciit snffer extensive fragmentation, resulting in a c h i d of opaque particles that diffuse into the
Iwra tiiiized rct icnlum of the first-type ducts.
~ ESVA F r r r ERE I) 4s a rA c; LA SDS
Opening into the annl wall intlepeiitlciitly of tlic three large
capsulated glands arc gromps of small miieoiis glands of the
tuhnloracemose type. They are liiic~tlh t l i in the alveoli and
the chwts by a cubical secretory el)itlwliiim iwtiiig oii a hase
meiit mr?m\)rane. Tlio iinclcus lies in the basal portion of tlic
c ~ l l snext tlie basement ‘I’lie cytoplasm is faiiitl:
gra nu1a r . No tlosqu ania t i ( ) 1 1 ( ) w i i r s i i i t 1iese gl ;i1 I ( IS . ‘r1I ey
appear. to bc mucous glands, and their presence side by side
with the large glands upon tlic anal wall is uscfnl to show
that the latter are definitely not cierivcd from mucous glands,
from which they differ most markedly in possessing the characters described in this paper.
In Citcllus ricliarclsonii three large glaiid masses, one metliaii and veiitral, two lateral, ope11 npon the aiinl wall by
evertible clia~riielsrepresenting iiivagiiiations of tlic epidermis, the stratum coriienm of which is greatly thickened. Thc
cliaiiiiels are normally introverted, but wIie11 turned out they
appear R S three conspicuous papillae. Tlie glaiicl masses are
surromidccl b)- a sheath of striated muscle proloiiged inward
into septa between the glands ant1 derived from tlic sphincter
aiii externus. Tlie retraction of the papillae is effected hy
mistriated muscle derived from tlic loiigitiidiiial musclc coat
of the large intestine which is prolonged clowii into the anal
eaiial. ‘l’he glaiitl masses comprisc two distiiict liistological
elemelits, both represeiiting modified sebaceous glands, thc
hair follicles of which have becn lost. Lobules of one type
constitnte tlie bulk of the glaiitl aiitl cwiisist of alveoli tleiisely
fillccl witli epitlielial cells in the course of closquamatioii. The
sccoiicl type of glaiidular tissuc comprises a smaller number
of lohiiles lyiiig bet.ween those of thc first type and the mnscnlar capsule. ‘l’heir alveoli possess an open lumeii into which
fluid is sccretccl and cells are shed from thc walls concomitantly with secretion to form corpuscles n-liich undergo degenerative aiicl cytolytic cliaiiges, some of them encysting first.
Tlie ducts of these alveoli are long and branched and pass
hetw-eeii tlie lohules of tlie first type to opcri to tlie exterior
together with the clncts of the latter. Active clescpiamation
of epitlielial cells takes place iii both kiiicls of alveoli t o
form a spoiigy kcratiiious mass in ~diicli is coiitaiiietl
the fluid portion of the secretion. Discharge of secretioii
ant1 pi-otrnsioii of the papillae seems to be associatd
mitli the tlefeiise liahits of the aiiimal. The fluid is of a pale
I)ro\vii or creamy color, containing in suspension tlie cornified
remains of cpithelial cells and encysted corpuscles. It appears to be odorless and non-acrid.
This paper is confined to the morphology of the glands, but
it i s hoped that further investigation into the nature and
function of the secretion will be possible at a later date. I n
tlio meantime it is suggested that the glands may function
partly as organs for tho excretion of keratin.
A clieinical slutlv of the sccrction of tlie an:d glands of
3lephitis mephitieit. Jour. Esp. Mecl., 1896, no. 2.
I. 1911 The anal g h n d s of Mephitis mephitica. Anat. Rec.,
vol. 3. no. 11, pp. 497-523.
1873 Castor glands of tho bearer. Proc. Acad. Phil., p. 440
CHATIS, J. 18i-k Ghndes odorantcs dcs Slanimif6res. Ann. Be. Nst., (5) xis.
AND KEPNER1908 Principles of animal histology. Macmillan, N. Y.
GKOSZ, S. 1904 UbCr den 1’erineals:ick von Caria cobnya und seine Driisen.
Zcitscli. wiss. Zool., l3d. 78, S. 261-267.
IIhlirmr,, TI. I 9 2 3 Zur Rrnntnis in der Analgrgcnd bci Insektivoren vorkommciitlcn Drusen. An:Lt. Anx. J e n a (Vcrlr. ilnat. Ges.), Bd. 57.
l l b i < ~ t t G.
~ ~ , 1899 8ur Iex glandes itnalrs du chien. Ann. de Mod. Vet., T. 48,
111). 633-641.
IIr-tcm. (;. C., AND ADAMSON,11. W. 1903 A4contribution to the morphology of
sudoriparous and allied glands. Contrib. Yea. Sc., Ann Arbor.
MI. wfi;\ou-i~rscH. TJ. 1907 \7crgleichende anntomisclie Untersuchungen uber
die Rcgio nnalis, und das Rectum der HaussLugetiere. Inaug. Diss.
Leipzig, S. 1-152.
Poc*ocii,R. I. 1913 On the feet and glands and other external characters of the
Tiverrinae. Proc. Zool. Soc., 191.5, pp. 131-119.
R a s r r ~ r t 1900 Histologic do Lz peau. Arch. d’anatomie, T. 3, p. 1.
11 WTIIEK, 31. 1903 Betnerkungeii uber den Gcnitalapparat nnd die Analdriisen
der Chiropteren. Anst. Anz., Bd. 23, 8. 495-507.
IlosFxsTuvr, 13. 1892 Internst. Moiitlilp Jour. Anat. and Physiol., vol. 9 (re
kci:itinizstion of sebaceous cells).
St i i wm, E. h. 1912 ’1’rxt-l)ook of microscopic anatomy. Longmans, Green,
T. S. I896
_ _ _ 19%) Essentials of histology, 1 1 t h ed.
Len & E’ebiger, New York.
LTntersuchungen rles Annltegumentes des Hnndes. Arch. f. ‘I’icdreilk, 13d. 30, 8. 472-5G.
% I \I V I : P ~ I A X
1 View of the posteroventrnl surface of the animal with the papillae protruded.
1, anal apcrture proper; 2, lcft lateral papills; 3, right lateral papilla; 4, mcdian
papilla ; 5, genital aperture (male; testes retracted).
2 Anal region with protruding papi1l:ie magnified.
3 Tiew of relxxed :inus, sliowiug position of openings of the c1i:cnnels fornied
by the introrrrsion of the 1):ipill:ie. I , anal c:inal; 2, 3, 4, right, median. nnd left
gland apertures, respectively.
4 Dissection to show lowrr portion of tlir rectum and inside of skin with
the glandular mass. 1, rectum, cut; 9,3, 4, right, median, and left anal glands,
respectidy, forming a tripartite mass; 5, inner surface of skin; 6, position of
genital aperture (eicised).
.5 The g1:tndu stretched : I W : I ~ l ~ ytlicir funduses from the rectuni.
ti Longitudinal section through one of t h r three glands. The iiitrorertiblc
rliiinnrl of the gliind is cut lengthwise, n fold ill its wall being sectioned tangnitially. The stratum corneuin of the cliaiincl is frayed out near its base, t o
Iiccoine continuous with tlie desquamated epithelial reticuluni of the first-type
h b I l k 5 wliicli :ire seen clustertd in a group of about eight round the base of the
cli:iiinel within the muscular inrestment. Situated peripherally and outside the
first-type eleinents :ire to be scen three groups of second-type alveoli. A seeondtype tluat is shown :it 5 near t o its eiitiy into one of thc larger first-type d u c t
mouths. A portion of tlie 1atcr:il retractor ligament is shown at 11. 1, debris in
iiioutli of c1i:iiiiiel; 9, tnrigenti:il section of a fold in the wall of cEianiie1; 3, rrtiruluin of dtwiuamnted cells ; 4 areolar tissue wliicli is prolonged between tbc
lobules; 5, second-type duct; 6, first-type duct; 7, second-type alveoli; 9. outer
muscle d i t v i t h ; I ( / , iniiei niiiscle she:itli ; 1 2 , rdrnetor ligament ; 12, derm:il
p p i l l n e in rete inueosuni of c1i:innel wall : IS, :iIreolus of first type.
7 liransr.erse section through the whole gland mass. The division into three
is seen. The three glands are surrounded by a sheath of striated muscle whose
double character is t o be seen best at tlie sides ( 6 , 7 ) . The two types of glandular elements can be distinguished together with their duets. I n the middIe gland
the channel is seen, the c.lrannels of the lateral glands n o t appearing a t the leyel
of the section. 1, channels; 2, second-type lobules; 3 , 3, second-type duct,;
4, stmtnm comeurn of channel ; ii, trirailintc connective-tissue ,j tmctiori of epin i y i a ; 6 , inner muxcu1a.r c o a t ; 7 , outer (comnori) coristrictor coat; 8, secretion
mass in cha.nnel.-just below, a. srnall portion of t.he wall is cut tangentially;
9, 9, murrcu1:ir septa; lii, lobule of first, type.
iwidcrcd differeiitly in flir drawing. 'I'lie
The two t;vpcs o f gtnnd-clcmciits
secorid.tyyr iilrruli itre rel)rewiit(~dby cue11 rings; thc first-type arc thickciied on
one side. Cornpaw 2 3ibd 10. Thus the t%o t.ypt3 citii be tlistiirguislied anywhere
iii tlie figure.
8 Section a t riglit angles t o the anal canal a t the level of the entrance of the
three chnnnels (retracted condition). The clevelopment of the sphincter ani
extc.nius into f:isciruli surrounding the channels is shown; to right and left are
seen tlic thick muscle masses a t the junctions of sphincter proper and constrictor
coat. In the loose connrctive tissue surrounding the channels are sebaceous
g1:inds and liiiir follicles from the adjacent skin. An extracapsular gland is
shown a t 10. I, :inal canal; 8, 3, 4, channels of the glands; 5, sphincter ani
esternus; 6, thickened portion of muscular sheath a t junction with sphincter;
7, tract of unstriated muscle running in adjacent panniculus adiposus; 8, dermal
papillae in epidermis of channel; 9, hair follicle; 10, extra capsular gland; 2 1 ,
striated fibers of constrictor coat, which here is very diffuse, bands of it running
across the panniculus; 12, panniculus adiposus ; 13, duct of extracapsular gland;
I f , nolniel se1)aceous gland ; 35, thick detached portion of stratum corneum in
Loiigitutliii:I I sectioii tlilongli w i l l of c1i:iiinrl near its 1):ise, to show tlie
out of tlit. str:itum eoriieuiti : r ~ ;lie
pronounced dcsquani:iticiii of the
rete ~nurosiim, the s1ic.d off mass heroming higlily vacuolzted. 1, region of cii1 : 1 r g ~ drpithdi;il wlls of retc Inucosum; 2, outer seal;v portion of stratum eori i v i i n i (thr iiiiniernl 2 is in the lumen of tlie channel) : 3, v:ieuol:itions hi the
~1csclri:iin:itctl tn:iss : 4 . wtc. niii(+osiirn; 5, stratum eorneum ; 6, stwtum granulosum.
10 The retractor muscles and ligament of the median gland near the anal
wall. The position of the anal canal is indicated by the sphincter ani internus
a t 1; several longitudinal fasciculi run toward the base of the ligament, though
its exact junction with them is not shown a t this lcvel. The interruption of the
constrictor muscle by the 1ig:rmcmt is shown and the insertion of the sarcolemmas
of the former upon the latter. I , sphincter ani internus (edge o f ) ; 2, fasciculi
forming retractor muscle of median ligament; 8, median retractor ligament ;
4, connective-tissue reticulum of the median gland into nhich the fibers of the
ligament merge ; 5, constrictor (striated muscle).
11 View of median retractor ligament, this time on the side of the gland
away from tlrc anal canal (it liris now circled the fundus of the gland since we
s a w it in fig. 9 ) . At tlie top of the photograph is the connective-tissue capsule
outside the muscular capsule, containing a few flattened masses of lymphoid
tissue (dark). The ligament is seen crossing the constrictor muscle at right
angles as before. At the bottom of the photograph is seen the channel of the
median gland.
1% Oblique section (low power) through tlie lower portion of the rectunr,
t o show the lateral retractor ligaments. (Tlie retractor ligament of the median
gland appears at a lower level and does not show in this section.) I n the t o p
of the photograph is seen the mucous membrane of the rectum thrown into
ridges. The circular muscle coat (sphincter internus) is shown a t 1, and immediately outside that the longitudinal coat, a t 0. The longitudinal coat can be seen
prolonged down from 2 to be inserted into the group of diverging connec.ti\(stissue fibers a t 7, 7, which spread out into the connective-tissue reticulum surrounding the lobules of the two lateral glands. The sphincter ani externus is
prolonged into the thickenings of striated muscle in the corners between g1:nids
1, sphincter :mi internus ; 2, longitudinal unstri:itett
and an:il canal.
coat; 9, sphincter ;mi externus; 4, luinen of rectum; 5, mucous membrane; 6, submucous coat of wctum; 7 , 7 , lateral retractor ligaments (appearing as strands
of connective tissue) ; X, cliunnel of median gl;inci; 9, junction of common mu#cular sheath and sphincter ani externus.
13 High-power view of a duct of first type 1ol)ule. I t s =all consists of a rete mucosum, whose cells, like those of the alveoli, undcrgo desquamation to join the
spongy keratinous reticulum. The v:iculations in the reticulum are occupied by
fluid together with the coipusrles formed in the second-typc gland. One of these
corpuscles, encysted or highly kerntinized, is shown :it 9. Photograph. 1, an adjxcent first-type duct; 2, strands of reticulum; 5, encysted eorpusclc which has
entered the reticulum of the first-type glands froin tlie second-type glands; 4 ,
vacuoles ; 5, retc mucosnm of duct wall.
14 Transverse Section through one of the lateral glands, to show the relationship of first-type and second-type elements. An agglutinated secretion niaw
is present in the second-type duct, which is thereby distended. Tlie conimnn
constrictor muscle is to be secn to the riglit and aliore. Tlie individual inner
coat is hrgcly incomplete here. The muscular septum separating the median
gland shows on the left and its double cliaracter is apparent in its upper portion.
1, first-type glands ; 8, second-type glands ; 3, constrictor sheath; 4, agglutinatrd
secretion m a s s in second-type duct; 5, niuscubr septum.
15 Section tlirorigh i i n outer portion of the first-type gland elements, showing
:i weond-tj pe duct cut transversely.
The connective tissue is strongly developeii
:IS :L sheath around the duct cstcnding upwaid :rii(1 to the right b e t ~ ~ ctliv
tirst-type alrcoli. Photograph.
l f j Hectioii tlironyli :i poi tion of sccontl-tylw glnnd, to show smernl :(I! eoli
opcning iiito :I ctuct. Tlie w i l l of the duct is cwmposcd of several layers of compact stratifietl cells which c h n g e al)ruptl;v in e1i:ir:icter where they beconic
coiitiauous with tlie mills of tlie :iIveoli. \Vitliin tlie ill\ eoli and the duct :ire
:igglutiii:ited inasses consisting of the tlegcncratioii products of thc cells of the
alvcoli. The changes which take p1;ice i n the secretory cells prior t o shedding
:ire illustrated (see t e s t ) . S o t c the 1:trge clulr-shaped processes into which the
free eiids of the cells :IYC tliawii. I , secretion ni:rss; 2, nrco1:ir tissue formiiig
fr;rinework betwee11 t h e :ilveoli; 3, s1ni1111 cliii ; 4 , h s e m e n t membrane; 5 , epithelial
cell ~fiissiiigout into lumen of :ilveolus: 6, nucleus; 7, i i n epitheli:il cell ivhieli
Iias Iieeii shed iiito lumen of :iIrcolus, sirwouiidrd by secretion n1:tss.
1 7 Corpuscles tlerireil f r o m the secontl-t
:rlveoli. The figures illustrate
some of the typical clianges i~+ic+lioccur in the cells during the process of
desqu:imntion and disintegr:ttion.
In A ;in epithelial cell of the liniiig of tlic alveolus is lrrcoiniiig onlargrtl
~ u q r : i r : i t o i ~to- its dctncliinent fioni tlic \\:ill. The cytoplasm is becoming cleaier
nnd inoi-e fluid as indicated by the glol~u1:rrsh:ipc. The nucleus is partly filled
with fluid, the rcsult of clirom:itolysis, aiid the rem:iiiiing c*hroinatiii has brokm
into two n ~ ~ s s e s .
In I3 :I clrt:ic*lictl cell 1i:iw 1)ecorncs almost entircl,~fluid, :nit1 lins developed n
I-! s t wall.
(’ :ind R illustrate :I i*onimoii c*oiiilitioii to 1)r olmrvctl.
The nuclear contents
h:i\ e : ~ s s u n i e d the forin of :I curvet1 bolitl I)ounded by portions of two spheres,
so that the dark ni:iss is roughly ~ o n v e soutw:nd and coneave toirard the space
filled with fluid that constitutes tlie re~ii:tin(lerof the nnclr:w cavity.
D il1ostr:itrs the protrusion of the nuclcus wliolr.
P shows the expulsion of the nuelens in fragments.
18 View of :I corpuscle from the sc.eonil-type alveoli wliicli has become emI~rddrd in the rete niucosum of :] first-type duct in a state of enqstinent :rnd
e division. In :ill of the divisitrn 1)roducts cytol?sis is going on.
19 IXagramniatic rrpresentation of tlie anal glands in the retracted condition.
I-cntrsl aspect, the anal canal being hidden froin view oyer a portion of its
rourse by tlio metli;rii gland. "lie g1:ind on the left is sectioned down its middle,
to sliow the relationship of the constrictor muscles t o the rectum. The median
gland ia c u t away on the lrft. The right gland is not shown except f o r its channel. I, skin; 3,upper portion of sphincter m i externus; 3, anal orifice; 4, outer
constrictor e w t ; 5 , inner constrictor coat; 6, cliiinnel of left gland; 7, first-type
g1:intl elements ; 8, second type gland elements ; 9, keratinizcd secretion mass ;
10. secwiid t y p dncts ; 21, rircular musclrs of rectum, continuous with sphincter
iini cxteriiiis ; 1 Z, 1ongitutiiii:il ninscuhr coat of rectum ; 13, inner circular
nicisclo; Id, lunicn of rcctmn; 25. anal canal, exposed: 16, channel of
nictli:rn glancl entering anal c:tn:il : 19, c*ii:innel of right gland; 20, median gland;
! I , c u t :iwa of nietli:in gland.
20 I)i:igraiiiiii:itic. it,~)l.esciit;itioiiof t l i c :iii:~lglands in the everted coiiditioii.
The coiistrietor coats are coiitr:icted, pushing out tlie gland masses aud csnsiiig
t h o cliaiiiicls t o turn i n s i t l ~ont so tlmt they now :ippear as papillae filled witli
the glsndukir tissue. Tlie t w o types of glandular elcinents are shown, the seeorultypo ducts being iiow w r y e1ong:ited. The figiire illustrates the retractor liginieiits :ind tlit, coats of the rcctuiii to tlislhy tlie relatioiisliips described iii tlic
tcxt. The :ispect is wiitml; lrciice the aiiiis is hidden from view 11)- the n i e d h
gland. 3 , secretion niaRs being dischaigetl ; ‘1. loose connective tissue; 3. inner
constrictor coat ; 4, median 1etr:ictor 1ig:iiiieiit; 5, retractor fasciculi; 6, sphincter
ani externus; 7, loiigitudiiial muscle coat of reetniii : 8, sphincter ani internu\ :
0. riglit lateral retractor ligaiririit ; 10, conixrion constrictor r o a t ; 27, filst-tyy~c.
Iol~iile;12, second-tvye lobule; 73, sccoird-type duct.
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adults, anatomy, grounds, histology, anal, sabine, gland, citellus, richardsonii, richards, squirrel
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