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The vascular architecture of tubular bone in the rat.

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Department of Anatomy, University of Liverpool, England
I n their recent paper on the vascularization of rabbit tubular bone, Brookes and Harrison ( '57) claimed that the cortex
receives arterial blood from what they term a medullary arterial system whose terminal twigs enter the cortex at its endosteal surface. Blood flow in compact bone was emphasized to
be from within outwards. I n order to determine whether this
feature of bone vascularization is typical of mammalian bone,
it was felt desirable to investigate the vascular architecture
of tubular bone in another morphologically different mammal.
The rat was selected as fulfilling this condition because it is
a readily available laboratory animal separated by some 60
million years of evolution from the Lagomorpha.
Fifty-six fully grown albino rats, average weight 350 gm,
were sacrificed in the course of the investigation by chloroform overdosage. The vascular anatomy of the rat femur and
tibiofibula was investigated firstly by gross dissection in order
to examine the multiple blood routes available to these bones
apart from the principle nutrient artery. Micro-radiological
and histological techniques mere used to elucidate the intraosseous vascular arrangements in the same two bones.
Fifty-one rats were injected intravascularly immediately
post mortem with the radiopaque medium Micropaque (Damancy & Go., Ltd.), a 50% suspension of barium sulphate whose
average particle size is claimed to be 2 p. Because of its high
viscosity, it was found necessary to dilute it 50% to produce
arteriolar filling, and 60% dilutions were essential for radiographic visualization of capillaries in bone cortex.
To fill the arterial system of the hind limbs, the abdominal
aorta was cannulated with polythene tubing through which
10-20 ml of Micropaque were injected at 70-100 mm Hg
pressure. Adequate filling of long bones coincides with complete filling of the vessels on the gut wall. Injection of the
venous system of the leg was effected by introducing a No. 14
Record needle into the external iliac vein, and passing it
distally so as to pierce the venous valves in the femoral vein.
The needle was then tied i n situ and Micropaque injected
through it retrogradely into the veins of the limb. As an
auxiliary procedure f o r venous filling, the long saphenous
vein was injected at the ankle joint after ligation of the internal iliac vein. Valves are few and weak outside the main
femoral venous valves of the rat hind limb. Following injection the lower limbs were removed together with the
pelvis in one piece and fixed in 57% formol saline. After fixation, Micropaque is quite firm and does not run. By virtue of
its white color, the part could easily be dissected to determine
every vessel that pierced bone, the sites of penetration being
recorded. A binocular dissecting microscope considerably
facilitated the gathering of observations which were collated
from 16 dissections.
Material for radiographic analysis was prepared with Micropaque as described above. Following fixation the individual bones were stripped of all extra-osseous tissue including
the periosteum and decalcified in a 5% nitric acid solution.
Rat femora and tibiae thus prepared were microradiographed
on Kodak maximum resolution plates using a microfocus
radiographic unit incorporating the Ehrenberg and Spear
tube. The bones were examined either whole or in thin slices
(1.0 mm) cut by hand.
For histological study, the hind limbs of 5 rats were fixed
in Zenker-formaldehyde and embedded in low viscosity nitrocellulose (L.V.N., Chesterman and Leach, '49). Transverse
and longitudinal sections were cut at 20 p and stained with
carbol thionin-picric acid (Schmorl), or with hematoxylin and
Gross observatioias
The arterial pathways subserving the rat femur and tibiofibula are drawn in figures 1to 4,the nutrient arteries actually
piercing bone being shown in relation to their larger trunks
of origin. The explanatory keys use a nomenclature based
wherever possible on that of Greene ( ' 3 5 ) .
Attention is drawn t o the dual arterial supply of the femoral head from lateral circumflex femoral and obturator arteries. These give origin to anterior and posterior subcapital
arteries which are joined by a circulus arteriosus capitis
femoris (figs. 1 and 2) from which tiny arterial twigs enter
the head from the whole circumference of its rim. No arteries could be traced in the ligamentum teres as far as the
The principal nutrient artery of the rat femur arises
regularly from the lateral circumflex femoral artery and
enters a prominent canal on the medial surface of the shaft
below the lesser trochanter. I n two femora a second, much
smaller diaphyseal nutrient artery pierced the anterior face
of the femoral shaft. The arterial supply of the inferior
femoral epiphysis is a triple one, the superior lateral genicular, the middle genicular and the A . suprema genu. The
greater and lesser trochanters have each one main artery,
the lateral and the medial circumflex arteries respectively.
The third trochanter has no nutrients.
Because of its composite nature, the tibiofibula has a more
complex arterial supply than the femur, the complexity lying
in the formation of numerous anastomoses and arcade systems (figs. 3 and 4). Nevertheless, the vessels supplying it
can be reduced to the A . suprema getzu, the inferior media1
and lateral genicular, anterior tibial, peroneal and saphenous
arteries, 6 in all. The principal nutrient artery is derived
from tlie amterior tibial, and enters the tibial shaft just above
the synostosis. The shaft of the fibula possesses no principal
nutrient canal. The lower half of the bone is remarkable in
that it is surrounded by many large arteries passing into the
Abbreviations used in figures 1-4.
L.P..4., lateral plantar artery
A.A.F., artery t o acetabular fossa
A.B., articular branch
L.S.A., lateral sural aretry
A.C.L., anterior crural liganlent
M.B., muscular branch
A.I.A., auterior intercondylar artcry
M.C.F.A., medial circumflex femoral
A.L.T., artery to lesser trochanter
A.S.A., anterior subcapital artery
M.G.A., middle genicular artery
A.S.G., arteria suprema genu
M.H.A., middle haemorrhoidal artery
A.T.A., anterior tibial artery
M.M.A., medial menisceal artery
AN.>’., anastomosis around fibula
N.P.D., medial plantar artery, deep
AS.T.T., anastonlosis round third trobranch
A.T.R.A., anterior tibial recurreilk
M.P.S., medial plantar artery, supcrartery
ficial branch
C.A.C.F., circulas arteriousus capitis
N.S.A., medial sural artery
M.T.A., medial tarsal artery
C.S.A., common sural artery
N.I., nutrient to ilium
F.A., femoral artery
obturator artery
Fab., fabella
Pat., patella
F.B.P.A., fibular branch, peroneal
Per.A., peroneal artery
H.F., head of fibula
P.E.T., pudic epigastric trunk
HPP.T., hypogastric trunk
P.N.A., principal nutrient artery
LA., intercondylar artery
POP.A., popliteal artery
I.L.G.S., inferior lateral genicular
P.S.A., posterior subcapital artery
P.T.A., posterior tibial artery
I.M.G.A.. inferior medial genicular
SAP.A., saphenous artery
S.C.I.A., superficial circumflex artery
I.P.AN., infra-patellar anastomosls
S.L.G.A., superior lateral genicular
L.C.F., lateral circumflex femoral
L.C.F.A., lateral circumflex femoral
S.M.A., superior muscular artery
artery, articular limb
S.M.G.A., superior medial genicular
L.C.F.D., lateral circumflex femoral arartery
tery, ascending branch, dorsal
S.S.A., superficial sural artery
J,.C.F.V., lateral circumflex femoral ar- SU.L., lateral supracondylar artery
SU.M., medial supracondylar artery
tery, ascending branch, ventral
V., opening for emissary venous sinus
The gross anatomical arrangement of the veins of the rat
femur and tibiofibula is similar to that of the arteries. Each
artery has its own single vena comitans. At bone extremities
there are more emergent veins than entering arterial twigs.
A. S.
S. M. G.
Fig. 1 Drawing of arterial supply of the rat femur; anterior aspect.
An. T. T.---
A. 6.
Fig. 2
Drawing of arterial supply of the r a t femur; posterior aspect.
Some of these veins therefore do not share their canals with
incoming arteries. The femoral intercondylar vein does not
accompany its artery, but joins others issuing from the superior tibia1 epiphysis to form the inferior lateral genicular vein.
Fig. 3 Drawing of arterial supply of the rat tibiofibula; anterior aspect.
Two large foramina are found in the posterior surface of the
upper tibial metaphysis which lodge emissary veins draining
into the anterior tibial vein. The latter also receives as tributary an unaccompanied vein issuing from the fibular side
of the shaft below the synostosis.
Fig. 4 Drawing of arterial supply of r a t tibiofibula; posterior aspect.
Radiological obsercatioszs
Because the radiographic appearances of rat long bones
following intra-arterial injections of Micropaque are complex, in that the venous as well as the arterial side of the
circulation are thereby visualized, the results of pure venography mill be described first.
Veins. The upper metaphysis of the femur comprising the
neck and most of the head, is predominantly drained by a
single centrally situated, cervical vein passing down to the
intertrochanteric region (fig. 6). Here it joins other veins
arising in the greater and lesser trochanters to form the
upper extremity of the central venous channel of the medulla
(fig. 13). This vessel preserves its single identity down to the
lower end of the bone where it gathers up the venous sinusoids of the inferior metaphysis and breaks up into the small
veins issuing there from the bone (figs. 6, 8). Occasionally
it divides into two stems low down in the shaft. Below the
lesser trochanter, the principal nutrient vein forms a prominent branch of the central venous channel which exhibits
transversely disposed radicles throughout its medullary
course (fig. 14).
Microradiography of transverse and coronal sections of
the femoral head filled by retrograde venous injections of
Micropaque, show a remarkable disparity in venous lay-out
between the metaphysis and the superior epiphysis overlying
it. The former is full of irregularly disposed venous sinusoids of relatively large caliber showing numerous varicosities
and interconnections (fig. 15). The thin epiphysis on the
other hand, fitting over the metaphysis like a cap, is drained
by fine, transversely disposed venous channels which are
gathered up to form veins issuing at the superior (lateral)
part of the capital circumference (figs. 16, 17). A transverse
venous channel in the femoral condyles (fig. 18) is a peculiar
feature of the inferior epiphysis also. Sections cut so as to
include the foeea capitis feworis do not shorn any obvious
venous channels issuing there into the ligamentum teres. Al-
though the epiphysis and metaphysis drain into separate veins,
there are vessels uniting the two vascular territories (fig. 16).
The main intra-osseous venous pathways of the tibia are
essentially comparable to those of the femur. A central
venous channel of the medulla extends from the lower of the
two foramina found on the back of the upper tibia1 metaphysis, and passes downwards to break up into the venous sinusoids of the inferior metaphysis. Prominent branches are
formed by the principal nutrient vein, and an isolated peroneal emissary vein below the synostosis (figs. 11, 12). The
upper metaphysis is largely drained by a well defined channel which issues from the upper of the two foramina mentioned
above (fig. 22). Horizontal venous channels are found in both
epiphyses (fig. 20). I n the medulla, fine hair-like tributaries
of the central venous channel are evident in profusion.
Arteries. I n radiographs of femora and tibiae injected
through the arterial route, venographic appearances provide
a background from which the following intra-osseous arterial
features of the circulation can be elucidated.
In the femur, the principal nutrient artery divides on entering the medulla into ascending and descending stems, the
latter especially showing extreme tortuosity in the course
down the shaft of its two main subdivisions (fig. 10). Adjuvant metaphyseal arteries are seen supplying the head
and neck of the femur (fig. 7 ) and the inferior femoral metaphysis (fig. 21). The latter microradiograph is of a sagittal
section taken through the intercondylar notch which together
with figure 23, an arteriograph of a companion condyle, demonstrate independent circulations in the metaphysis and epiphysis. Whereas in the former, medullary arteries are
arranged vertically and break up into a dense mass of venous
sinusoids, the epiphysis shows an almost wholly arterial picture, only slightly obscured by the presence of a large transverse venous channel. The pattern of arterialization in the
epiphysis is that of fine arterial twigs repeatedly subdividing
and radiating towards the articular cartilage. Some undoubtedly cross the epiphyseal line and disappear in the
metaphyseal sinusoidal mass. There is no evidence of arcade
formation in relation to the articular surface. The fine arterial channels of the juxta-articular zone are end-arteries.
The tibia shows essentially the same compound arterial and
venous picture on microarteriography as the femur. The ascending branches of the principal nutrient artery are larger
and more numerous than the descending ones (fig. 19). Below
the synostosis, a fine arterial twig sometimes pierces the
bone (fig. 12) independently of the peroneal emissary vein
which receives the central venous channel of the fibula (fig.
Transverse microradiography of rat diaphysis (fig. 24)
shows numerous medullary sinusoids converging on to the
central venous channel. Against this background, well-defined
tortuous arterial twigs can be clearly discerned diverging
towards the endosteal face of the compactum where they
terminate. Only a slight penetration of the cortex by medullary arterial terminals occurs. It is, however, traversed in
a radiate fashion by fine hair-like vessels, undoubtedly capillaries, which here and there can be seen arising directly from
endosteal arterial terminals. I n caliber they are finer than
the medullary sinusoids with which they appear generally to
he in continuity at the cortico-medullary junction.
Histological observations
I n transverse sections, the blood vessels of the compactum
appear to have no regular arkangement. Endosteal bone trabeculae form bays lodging medullary sinusoids in continuity
with the vessels of the cortex (fig. 26). Fine vessels which
pass out of the compact bone into the overlying periosteum
are identical in appearance both with the vessels in the intermediate cortical zone, and with those in continuity with the
medullary spaces in the endosteal zone. Cortical vessels are
more advantageously displayed in longitudinal sections of
the shaft (fig. 25). They consist of simple endothelial tubes
uniform in diameter (mean of 10 readings, 10.7 I.I) which are
geiierally parallel to one another and pass obliquely from
the medulla to the diaphyseal surface to aiiastomose with
periosteal capillaries and the interfascicular capillaries of
muscles with fleshy attachments to the bone. I n the upper
two thirds of the femur and upper third of the tibia the obliquity of cortical capillaries is downwards and outwards, but
Fig. 5 Diagram of the vascular organisation of rat tubular bone in longitudinal
section. A, artery; V, vein.
upwards and outwards in the corresponding lower portions
of these bones. They are directed away from the epiphyseal
growth cartilages and meet in a junctional zone of the shaft
having undergone a gradual change in direction brought
about by a kinking of their intracortical course (fig. 5).
I n longitudinal sections of the medulla, a central channel
is readily seen 152.9 p in diameter whose wall is composed of
a single layer of endothelial cells alone. Other longitudinal
vessels, 27.4 p in diameter, course through the dense surrounding medullary sinusoids. Their ~7alls are relatively
thick, and possess a muscular media.
The anterior surface of the shaft of the rat femur is pierced
occasionally by a nutrient vessel much smaller in size than
the principal nutrient artery which normally enters the bone
medially just below the lesser trochanter. Greene ( ' 3 5 ) regularly places the principal nutrient canal in the anomalous anterior situation. The head of the rat femur is not pierced by
arteries carried to it in the ligamentnm teres; its nutrition
depends on the medial and lateral circumflex femoral arteries
wvhose branches form a vascular circle around its circumference. There is a confluence of veins from the adjacent epiphyscs of fcrnur and tibia in the rat knee joint similar to
that obscrved in man by Langer (1876) who envisaged a
pumping mechanism at the knee mediated by alternate flexion and extension of the joint. The many large arteries passing into the rat foot are presumably essential clemeiits for
temperature control in this mammal.
The extremities of rat long bones are pierced by large numloers of small arteries whose total cross-sectional area must
bc large when compared with that of the principal nutrient
artery. Brookes ('57) has estimated that these vessels are
adequate for 97% of the growth in length of rabbit bones
from birth to maturity. The so-called principal nutrient artery is merely the largest of many concerned in the arterialization of bone. Together with metaphyseal arteries it forms
a medullary arterial system for the delivery of blood both
to the cortex and medulla of the shaft. I t s terminals abut
against the endosteal face of the compactum giving rise to
capillaries which permeate the cortex in a regularly oblique
fashion. The principal nutrient canal being subject to the
same growth factors as the cortical capillaries surrounding it,
is parallel to them. Medullary arterial terminals also empty
into the medullary sinusoids by means of funnel-shaped connections (Testut and Latarjet, '48) which were originally
postulated by Neumann (1869). As f a r as the present writer
is aware, they have never been histologically demonstrated.
The absence of vessels larger than a capillary in rat tubular
bone cortex is striking, an observation supported by T'eidenreich ('23). At the surface of the shaft they are continuous
with periosteal and interfascicular capillaries, and at the
endosteum with medullary arterial terminals and sinusoids.
Because there is only one vascular lattice in the cortex, it is
difficult to see how blood coming from the periostenm could
pass centripetally on meeting blood passing out of the cortex
from the medulla. Periosteal arteries, whose function may be
presumed to nourish the osteogenic membrane, are fern (Lamas, Amado and da Costa, '46) while endosteal medullary
arterial terminals are many, close up to and against the COTtex. When Hyrtl (1864) injected the human tibia through the
periosteal system alone, he failed to fill the medulla and
found that the cortical capillaries were still filled with blood.
Johnson ('27) in the dog, failed to stain diaphyseal bone
cortex with Indian Ink injected solely through the pcriosteal
system. Periosteal abscesses produced by Robertson ( '27)
by intravenous injections of Staph. aureus did not involve
the underlying bone. It would seem valid to conclude therefore that compact bone is supplied with blood from the medulla and not from the periosteum.
The venous system of the shaft is represented by endothelial tubes, either medullary sinusoids, or the longitudinal
central venous sinus and its branches. Arterial pulsation occurring in a fluid marrow confined in an incompressible tube
of cortex would result in milking blood from the sinusoids
into the central sinus and thence into metaphyseal and emissary veins (e.g., the peroneal in the tibia). Cut living bone
does not exhibit jets of blood (Lamas, Amado and da Costa,
’46) thus suggesting that arterial pressure within bone is
low. Venous pressure in tubular bone must be near zero
because of the wide avenues of escape presented by the venous architecture and not least the cortical capillaries. It may
well be that blood flow in compact bone does not only depend
on a vis a tergo; it is probable that attached and surrounding
muscles “pump” out blood from tubular bone by compressing
during functional activity the periosteal and interfascicular
capillaries and veins which initially are in direct continuity
with the cortical capillary bed. I f such a mechanism is a
factor in the maintenance of a normal circulation through
bone cortex, it follows that the pathogenesis of osteoporosis
during muscular inactivity (anterior poliomyelitis, splinting
of fractures) lies not in the cessation of “trophic” influences
but in a direct disturbance of cortical vascularization.
From the radiological evidence some anastomosis between
the epiphyseal and metaphyseal vascular systems seems likely
to take place across the epiphyseal line, although this could
not be definitely supported by histology. A transverse venous sinus and a radiating arterial pattern are peculiar features of the epiphyseal circulation. I n particular, those arterial twigs which pass dichotomously towards the articular
cartilage do not anastomose with one another; arcade systems are not present in the juxta-articular zone. It is known
that the fibrous structure of articular cartilage has a predominantly vertical disposition (Hunter, 1743). Most loose
bodies dehisced from joint surfaces do contain some bone as
well as cartilage (Wardle, ’57). It would appear that juxtaarticular arterial terminals are end-arteries nourishing a
tissue cone whose base and apex are cartilage and spongy
bone respectively. Lateral diffusion and overlapping of
metabolic fields in these minute conical regions no doubt occurs. Nevertheless, the anatomy of the epiphyseal circulation
provides support for an obstructive vascular aetiology in
osteochondritis dissecans.
1. The gross and minute vascular architecture of the rat
femur and tibia are described.
2. Rat cortical bone is irrigated by capillaries, whose blood
passes out towards the diaphyseal surface from a medullary
arterial system.
3. The importance of muscular activity in the maintenance
of a normal cortical circulation is discussed.
4, End arteries in the juxta-articular zone of epiphyses
are described and related to the problem of osteochondritis
diss ecans.
It is a pleasure to record the advice, assistance and criticisms of Professor R. G. Harrison during the investigation.
My thanks are due to Messrs. L. G. Cooper, A. Taunton and
Miss B. Birkett for their technical assistance and to Mr.
D. J. Kidd for the drawings. This project was aided by a
grant from the Sir Halley Stewart Trust.
JI. 1957 Femoral grovth a f t e r occlusion of the principal nutrient
canal in day-old rabbits. J. Bone Jt. Surg., J9B: 563-571.
M., AXD R . G. HARRISON1957 The vaseularization of the rabbit
femur and tibiofibula. .T. Anat. Lond., 91: 61-72.
CIIESTERMAN,W., AND E. H. LEACH 1949 Low viscosity nitroccllulose for embedding tissues. Quart. J. Micr. Sci., 90: 4 3 1 4 3 4 .
GREENE, E. C. 1935 The Bnatomy of the Rat. The American Philosophical
Soc., Philadelphia.
HUNTER,W. 1743 Of the structure and diseases of articulating cartilages.
Phil. Trans., 4 2 : 514-521.
HYRTL,J. 1864 Normale und abnorme Verhaltnisse der Schlagadern des Unterschenkels. Denkschr. Akad. Wiss. Wien., 23: 245-288.
R. W. 1927 A physiological study of the blood supply of the
diaphysis. J. Bone Jt. Surg., 9: 153-184.
L ~ M A SA.,
, D. ANADO AND J. ChLESTINO DA COSTA 1946 La circulation du
sang dans 1’0s. Pr. m6d., 54: 862-863.
1876 Uber das Gefasssytem der Rohrenknochen, init ReitrHgen zur
L ~ S G E KK.
Kuintiiis des Baucs und der Eiitwickluiig des Knochengewebes. Denkschr. Akad. Wiss. Wein, 3 6 : 1-40.
NEUNANN,E. 1869 Uber die Bedeutung des Knochenm:irkes f u r die Blutbildung.
Eiri Beitrag zur Eiitwicklungsgescliic'nte der Blutkorpercheii. Arch.
Heilk., 10: 68-102.
D. E. 1927 Acute haematogenous osteomyelitis. J. Bone J t . Surg.,
9: 8-23.
TESTUT,L., AND A. LATARJET 1948 Trait6 d'Anatomie Humaine. vol. 1. G.
Doin, Paris.
1957 Personal communication.
WEIDENREICII, F. 1923 Knocheiistudicn. I. Teil. Uber Aufbau und Entwicklung des Knocheiis und den Charakter des Knoehengewebes. Z. ges.
Anat. 1. 2. Anat. Entw. Gcsch., G9: 382-466.
13 Fcnirlr vcwogr:IIii. Vriious cliaiiiicls ill tlic, Iicck, greater :iiitl lesser trwliinrtcxrs
of the feiiiur Luiite t o form the upper end of the central venous sinus, witli
which the priiicipal iiutrieiit veiii is iii continuity. X 3.5.
Femur veiiogrnni showiiig a portion of the central venous sinus and its larger
tr:nisrcrse inedul1:rry tribut:rries. X 9.
Feniur ve~iograrn. Tliis eoroiial section through the lieail of the femur sliows
a rrutr:il area, beloiiging t o the upper nietaphpis, full of sinusoids of varicose :ippe:irance. Surromitling i t is :in :ninular portion of the superior rpipliysis with fragments of Iioii-siiiusoidal venous cliaiinels. X 18.
Feiiiur venogrnni. Tlic f o v e : ~ capitis ivas iiicluded ill this sagittal section
through the feriioral Iicnd. T lie iiidepciideiit nature of the circulatioiis in
the epipliysis and mctapliysis is slioivii. Some epiphyseal veins wliirh a r e
largely transversely disposed (lo 1 x 1 s ~iuto tlie iiirt:rpliyse:il siiiusoitlal iiiiiss.
X 15.
Fciiiiir rciiograni, slion.iiig tlir
Femur vcnogr:iiii, sliowiiig tlic hreakiiig u p of the central veiiaus sinus i n
the inferior nietal)liysis, aiid a tr:nisvcxrse siiius iii tlie iiiferioi rpipliysis. x 5.5.
Tibia arteriograui, sliomiiig how tlie priiicipal nutrient artery 1)
(to tlie right of the figuw) iiito tlic meclull:i, where i t breaks up iiito several
ascending branches. X 7.
Tibia veiiograin. Tlie su1)wior epipliysis of tlic tihia is sliown, contxiiiiiig n
transverse venous sinus. x i .
Feniur nrteriogram. A sagittal section h;is lreeii takcii tlirougli tlic intereoiidylar notch. Medullary nrtcrics arc shoirii passing vertically towards tlic
q i p l i y s c a l juiictioii tlirougli a mass of siiiusoids in the inferior
Tlic cpiptiysis, f r r c of siiiusoids sliows fine arterial vessels rntlinting towards the articular surfncc. Arcaclr formation is not iii evideilce. x 9.
Tihi:r rc~iograiii. This iiiconiplctc.17 fil!ctl specimeii shows Iiow t h r supc,rioi
tibia1 inetaphysis Iias its o n l i vriious siiius. Below i t is the upper r i d of the
eciitr:il vciious s i n u s of tlir shaft. X 7.
Femur artcriogrniii. The grrater part of a co~id,vleis slio\rn iii this figure.
Tlir wide cliaiincl i i i the infcrior epiphysis is a vein. Many fine channels arc
seen, radiatiiig toivnlds the articulnr cartilage, which have mi appearaure
suggestive of end-artcries. The two gray shadows to the left aud belon. the
bone are artefacts. X 9.
appearances as i n Fig. 16. X 15.
Feiiiur artcriograui. A transverse sectioii taken from tlie shaft, sliowiiig
dciise iiiedullary siiiusoids and slimply clcfiiicd medullary arteries. Tlic cortcr
is riddled with fine hair-like vessels coiniectctl nritli eiidostral :~rteri:iltc~rinin:ils
and venous siiiusoids. X 3G.
Longitudinal sectioii of bonc cortex staiiied with piciic :]rid aiid tliioiiiii.
Attached muscle fibers lie 011 tlie left, the medulla 011 the riglit of the figure.
Cortical capillaries permeatiiig the sectioii are gcuerally n r ~ i i g e dparaliei to
one aiiotlier and obliquely tlisposed. x 150.
Traiisversr sectioii of dinl)liyse:il cortex st:iiiied with picric. :wid :uid tliioiiiii.
The periosteal surface lies t o the riglit of the figure, the niednllnry to the
left. Three bone capillaries arc slioivn becomiiig coiiflueiit iii :I nicdul1:rry
siiiusoitl lodged in a bay foriiicrl bp eiidosteal trabec~iilne. x 1TO.
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architecture, tubular, vascular, rat, bones
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