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The effect of optic enucleation on the male albino rat.

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T H E E F F E C T O F OPTIC ENUCLEATION ON THE
MALE ALBINO R A T 1
LUDVIG GUSTAV BROWMAN
Department of Zoology, Montana State University, Mimoula
FIVE FIGURES AND TWO PLAT'ES (EIGHT FIGURES)
INTRODUCTION
It is well known that light stimulates the reproductive
system of the white rat (Browman, '37, '38 a ;Fiske, '39 ;LuceClausen and Brown, '39 b; de Jongh and van der Woerd, '39).
It has also been reported that light or the absence of light
influences the general growth of the white rat (Browman,
'38b; Luce-Clausen and Brown, '39 a). Just exactly how
light exerts its influence is not fully understood. Most workers
who have investigated the effects of radiant energy have
assumed that light acts via the optic apparatus to stimulate
the pituitary which in turn affects other organ systems.
If the eye, products of the eye, or portions of the optic
apparatus are necessary for radiant energy t o stimulate the
pituitary with the consequent release of gonadotropic, growth,
or other hormones, it may then be postulated that the ablation
of the eye would inhibit or delay the release of these pituitary
substances. If there is a delay or inhibition of pituitary
activity there should be evidence of such inhibition in the
morphological and physiological conditions of experimental
animals. Preliminary experiments along this line were previously reported (Browman, '38 a, '38 b).
This investigation has been supported in part by grants from American
Association f o r the Advancement of Science, Elizabeth Thompson Science Fund,
and Penrose Fund of the American Philosophical Society.
59
60
LUDVIG OUSTAV BROWMAN
This paper reports the results of an investigation of the
effect of different categories of visible light upon white rats
with the eyes removed at birth and upon their normal-eyed
litter mates. Observations on male animals primarily concern
us in this communication.
METHOD8
All animals used in this experiment were from a basic eleven
generation brother-sister inbred line started from a single
pair of animals from the colony inbred line at the Hull
Zoological Laboratory, The University of Chicago. Litter
mate males, from the thirteenth through the fifteenth generation, were equally distributed between normal and enucleated
categories under each given experiment.
All animals were weighed on the day of birth, on the day
of weaning (day 28), on day 100, and in addition once weekly
for the duration of the experiment. The food of the animals
on experiment I1 was a commercial dog biscuit, but all other
experimental and colony animals were fed B no. 21 ad libitum,2
plus lettuce leaves two t o three times weekly. Pregnant
females, lactating mothers, and young (until weaned) were
also fed a mixture of bread soaked in milk on alternate days.
After enucleated animals were weaned on day 28 they were
never placed in cages with normal-eyed animals. Competition
for food, in animals placed in groups, was only among likeeyed animals of the same age.
Animals which were optically enucleated always had the
operation performed during their first day of life, unless
otherwise specified. Normal animals and optically enucleated
animals in a given experimental series were always kept in
the same room, in the same size cages, and all other conditions
were maintained as constant as possible.
’B no. 21-ground whole wheat, 40 ; ground whole yellow corn, 15; powdered
skim milk, 17; Laeto-G milk powder, 5 ; meat meal, 5 ; wheat germ meal, 5 ;
dehydrated alfalfa leaf meal, 5 ; ground dried whole peas, 5 ; poultry yeast 5 ;
bone meal, 2 ; table salt, 1; salt mixture, 1. To 94 parts of above by weight
were added lard, 3 ; cottonseed oil, 2; cod liver oil, 1.
OPTIC ENUCLEATION I N THE MALE R.AT
61
Animals at sacrifice (ether) were weighed, and the organs
were weighed in the fresh condition and at once fixed in
Bouin’s. Sectioned preparations (4,6, and 8 p ) were stained in
Ehrlich’s haematoxylin and eosin, with alternate slides stained
with Mallory’s triple stain.
Measurements on the epithelial height of the seminal vesicle
were made on fifty cells selected at random from random
sections of the distal half of the seminal vesicle. The cell height
was always taken from the base of the nucleus to the plasma
membrane near the lumen.
Spermatozoa counts were made using one section selected at
random from sections cut a t random through the testis. Counts
were made of fifty tubules selected at random, care being
taken not to count the same cross section of any tubule twice.
A tubule was said to contain spermatozoa if it contained at
least five sperm heads, or spermatozoa (Moore, ’36).
The various experimental light conditions were as follows :
series 11, IVa, IVb, Vb-normal colony conditions ; 111,VIIconstant darkness ; IV, Va, VI-eonstant light ; IX-aIternating 8 hours of light with 8 hours of darkness. Sources of
visible light were ordinary 100 watt G E Mazda frosted lamps
suspended 18 inches above the floor of each cage. The only
visible light in the dark room was a single 15 watt frosted
bulb, suspended 6 feet above the floor, and used only during
the feeding and weighing of animals, and the cleaning of cages.
OBSERVATIONS
The condition of the mother’s eyes plays a part in determining the start in life a young rat will have, as measured
by the weaning weight of the young-. When 100 normal-eyed
young born to females which had been enucleated on day 1were
compared as to weaning weight with 100 young born to litter
mate females not enucleated at birth the weights were as
follows : 100 normal-eyed young from enucleated females41.4 gm. ; 100 normal-eyed young from the normal-eyed litter
mate females to above-45.3 am.
62
LUDVIG GUSTAV BROWMAN
The condition of the animal's own optic apparatus also plays
a part in determining its qrowth and development. For example, when 100 normal-eyed young from normal-eyed females
were compared as to weaning weight with 100 litter mates
cnucleated on day 1 it v7as observed that the normal-eyed
young averaged 47.7 gm. and their blinded litter mates 44.8 gm.
Thus it is seen that young from normal-eyed females hava
a better chance of approximating the normal weaning weight
of the colony (table 1)than do young from emcleated females,
irrespective of whether the animals themselves ape enucleated.
It has also been found that the young from microphthalmic
TABLE 1
Body weights of male albino rats
LIGHT
NUMBER
DAY 1
Nor. Enu. Nor. Enu
Col.
25
4.9
Col.'
8
9 5.0
Dark
8
7 5.1
Light
15 15 5.1
8 hours 3 3 4.9
D-N
l
5.0
5.1
5.1
4.9
DAY28
WEEK 8
Nor.
Enu.
h'or.
Enu.
49.4
40.2
47.6
45.4
51.0
142.1
40.8 121.7 108.7
47.4 129.0 113.7
44.7 112.2 97.6
51.0 139.0 138.0
WEEK
Xor.
205.3
184.7
186.0
184.6
211.0
12
Enu.
Nor.
Enu.
167.8
175.0
164.4
190.0
223.1
208.8
211.5
214.5
234.0
183.3
201.5
192.2
210.0
DAY 100
These animals were fed a eommercial biscuit; all the others were fed B no. 21.
females weigh less at weaning than ponng from normal-eyed
rats (unpublished).
All young reported in the following experimental series
were born of normal-eyed females.
Attention is called to the fact that regardless of the experimental light conditions the optically enucleated animals
averaged lighter in body weight at the same age than did their
normal-eyed litter mates of the same sex (table 1 and figs. 1
and 2). Since the different series were not all carried on at
the same season of the year the body weights are possibly
not directly comparable, even though all conditions were
kept as constant as possible. However in every instance
enucleated animals weighed less on day 100 than did their
normal litter mates on day 100.
BLINDED SERIES
111
Conatant dark
"....':,
_...'..-I-.-,*
....'
.
..
. .,
..
-Normal
famh
.----Blinded f enrle
......
N o m l mle
.-.-.-Blinded
male
1
3
2
5
4
6
7
8
9
l O l l 1 2 I 3
1 4 1 5
~ g ien reeks
Figure 1
BLIllDEDSERIpII
vb
Hormrl day-night
-(6)Bozaul eyed -18
..-(6)Bilrtenl enucleated m l e
- -- (6) Unilateral enuolaated male
1
2
3
4
5
6
7
8
9
Age in weeks
Figure 2
63
10
1 1 1 2
1 3 1 4
15
64
LUDVIG GUSTAV BROWMAN
It is possible that ablation of the eyeball and attached
muscles from an animal less than 24 hours of age may induce
injuries to the brain, etc., and thus delay growth. But by
referring to figure 2 it is seen that unilateral enucleated
animals grew as well as did normal animals; there was no
intermediate effect such as might be expected if severe injuries had been done during the operation.
It is common knowledge that in a colony of animals there
are individual variations in the rate of growth. Seven males
from three different litters which had been maintained in
single cages were divided into two categories on day 100:
the heavier males of each litter were lumped separately from
the lighter. The four heavier animals were enucleated on day
100 (fig. 3) while the three lighter animals were left intact
for another 5 weeks. The four heavier males gained an
average of only 6 gm. per animal in the 5 weeks immediately
following enucleation. During this same 5-week interval the
three normal-eyed litter mates gained an average of 35 gm.
per animal. The animals which had been the “runts” now
averaged 23 gm. heavier at 20 weeks of age than did their
four enucleated brothers. The operated animals did not lose
weight-merely had their rate of growth retarded.
Animals without eyes have no more difficulty in securing
food than normal individuals. When food consumption of
twenty-one normal-eyed animals was compared with that of
twenty-one enucleated litter mates, the average daily food
consumption for 39 trial days was found to be 14.2 gm. per
rat for the normal individuals and 14.3 gm. per rat for their
enucleated brothers. Furthermore, unsuccessful competition
for food can not be considered a factor in weight differences
between normal-eyed and enucleated animals because enucleated males in single cages weighed less than their normal-eyed
litter mate males similarly isolated.
The body lengths of normal and enucleated rats were found
to be approximately the same for’the same age. When the
animals from experiment Vb (fig.2 ) were measured at autopsy
on day 100, the following body lengths were obtained: six
65
OPTIC ENUCLEATION I N THE MALE RAT
*I
2
6
1
8
12
10
rr.
14
I".L."
Figure 3
aLmDDSERlrS I 4
norm1 day-night
3000
-i
-.
2
c
2500
2000
1500
1000
500
'
io
20
30
ao
Ag.
50
M
1" U Y .
m
80
90
100
16
18
20
22
24
66
LUDVIQ QUSTAV BROWMAN
normal-eyed-367 mm., six unilateral enucleated-365 mm.,
and six bilateral enucleated-364 mm. Enucleation theref ore
affects weight increase more markedly than skeletal growth.
0rgan weights
Autopsy on day 100 showed that male rats with intact
optic apparatus had heavier seminal vesicles, testes, and
pituitaries than did their blinded litter mate brothers (fig. 4).
The adrenals and the thymus, on the other hand, were heavier
in the enucleated than in the normal animals.
A series of male rats (experiment IVa) was killed at 5-day
intervals from day 25 to day 100. The difference in testis
weight between normal and enucleated brothers was first
evident at about 35 days of age (fig. 4). By the time the
animals reached 80 to 85 days of age the weight difference of
the testes was less marked. That is, there was a delay in the
growth of the testes of enucleated animals with an eventual
attainment of approximately normal conditions by 100 days of
age.
The difference in seminal vesicle weights was not apparent
until about 50 to 55 days of age. The weight of the seminal
vesicles of the normal animals was only slightly greater than
that of the enucleated animals until about that time. At that
time the accessories of normal males began to gain in weight
much more rapidly than those of enucleated males (fig. 4). It
is probable that the delayed growth and endocrine activity of
the testes is an indirect result of enucleation. The consequent
lowered production of testis hormone has directly prevented
the normal hormonal stimulation of the seminal vesicles.
Testis development
Examination of sections of preparations of the testis
made from animals killed a t intervals of 5 days revealed
a delay in spermatogenesis in enucleated males (fig. 5). The
first indication of the sperm head stage (Moore, '36) was
found in normal-eyed males 34 days of age. By 40 days of
67
OPTIC ENUCLEATION I N T H E MALE RAT
BLINDED SERIES
IVa
Uormal day-night
20.0
Seminal v e s i c l e e p i t h e l i a l height
19.0
18.0
17.0
I
16.0
f
2
x
15.0
14.0
I
13.0
/.
12.0
0.
I'
-brmal
enucleated
.-._Bilateral
enucleated
11.0
_._._.-.-.a
10.0-
Percentage of tubules with sperm heads o r spertUatOZOa
.-.-.
YO
-. -. _.-.-. -.- .-. -.-
I
80
I
I
70
I
I
t
3
60
I
I
8 5O
I
I
k
240
30
20
-Hormel
lo
enucleated
emcleat&
.-.- Bilateral
25
30
35
4.0
45
50
55
Days of
Figure 5
60
we
70
80
9a
68
LUDVIO GUSTAV BROWMAN
age normal males had over 50% of the tubules with sperm
heads and Spermatozoa, .while enucleated brothers had only
8% of tubules with sperm heads and no spermatozoa (plate 1).
Normal-eyed males had over 80% of their tubules with either
sperm heads or spermatozoa by day 45 while the enucleated
males did not reach a comparable stage until day 65 (plate 1).
It was not until day 60 that the enucleated males showed the
presence of even a small percentage of tubules with definite
spermatozoa. This is equivalent to a delay of approximately
3 weeks.
The cell height of the secretory epithelium of the seminal
vesicles as well as the presence of secretion granules and
secretion in the lumen have been used as criteria for male
hormone activity (Moore, Hughes, Gallagher, '30 ; Moore and
Price, '38).
Using the cell height of the secretory epithelium of the
seminal vesicle as a criterion of secretory activity, there is
no indication of an appreciable amount of male hormone
in the enucleated males until after day 50 (fig.5 ) . On the
other hand, the normal-eyed males revealed secretory activity
by 35 days of age (fig. 5) and reached considerable fuiictional
activity by day 40 (plate 2). A condition comparable to the
epithelial height of the seminal vesicle of a 40-day-old normal
male is not reached in the enucleated animal until approximately day 65 (plate 2 ) .
Apparently the delay in the production of male hormone by
the testis has been at least as great as the delay in gametogenesis in enucleated animals. The production of male hormone in enucleated animals as revealed by weights of whole
seminal vesicles shows that even at 100 and 150 days of age
it is not nearly as great as that of normal litter mates of the
same age.
DISCUSSION
Animals which had both eyes removed on the first day of
life consistently showed a retarded weight curve. It is
probable that the absence of the retinal apparatus resulted
OPTIC ENUCLEATION IIY THE MALE RAT
69
in a decrease in pituitary activity with the consequent production of inadequate amounts of growth hormone. LuceClausen and Brown ('39) report that animals kept in constant
darkness had a lower growth curve than did animals in visible
light. Animals kept by me in the dark with normal intact
eyes had a weight curve lower than that of the normal colony
while enucleated litter mate animals had a still lower weight
curve (fig. 1). It therefore appears that constant darkness
retards the normal activity of the pituitary, and that removal
of the optic apparatus has a more drastic influence. Young
born to females with eyes removed were lighter in weight at
weaning than were young born to females with intact eyes,
which may be interpreted to indicate inadequate lactogenic
hormone.
The evidence seems satisfactory that the operation per se
had no appreciable effect on the weight curve when we notice
the absence of any inhibitory influence on unilateral enucleated
animals (fig. 2). More careful work of an exact quantitative
nature should be done on food consumption and basal metabolism, but the evidence at hand would seem to indicate that food
consumption as such is not the important factor in the retarded growth of enucleated males.
It may be possible that with the lowering of certain aspects
of pituitary activity there is an increased activity on the
part of the thyroid and adrenal. When the voluntary work of
enucleated animals is compared with the voluntary work of
normal animals it is apparent that enucleated animals perform more work per 24 hours than do normal litter mates
(unpublished). This increased activity may account f o r part
of the weight difference. The skeletal lengths are apparently
only slightly, if at all, influenced by enucleation.
Organ weights
Certain organ weights of enucleated males were lighter
than the normal (Browman, '38 b). This same condition was
reported by Fiske ('39) to be true for males confined to constant darkness. With pituitaries, testes, and seminal vesicles
70
LUDVIG GCUSTAV BROWMAN
lighter in weight in the enucleated animals than in normal
animals we have additional evidence that the pituitary probably has been relatively inactive in the production of gonadotropic hormone.
DeJongh and van der Woerd ('39) suggest that it is possible to differentiate between the effects of winter and summer
light in that rats in the winter light conditions have lighter
and less well-developed sex organs than do rats in summer
light conditions. This difference was especially marked when
hormones were injected into animals-the hormones produced
a greater stimulating effect in summer light than in winter
light.
The heavier thymus characteristic of the enucleated animals
is the expected result in animals with delayed sexual maturity.
No explanation is advanced at present to account for the
heavier adrenals in the enucleated animals.
Testis development
Rrowman ( '37), Fiske ( '39) showed that increased light
stimulated the reproductive systems of rats, whereas constant dark did not have this effect. Fiske ('39) further reported that pituitaries from female rats in constant light had
a higher F.S.H. and lower L.H. content than pituitaries from
females in constant dark.
Microscopic examination of the testes of enucleatcd rats
showed that spermatogenesis was delayed approximately 3
weeks. Since the secretory epithelium of the seminal vesicles
showed a concomitant 3- to 4-week delay in development, it is
probable that the production of male hormone was also retarded. This histological evidence gives further support to the
suggestion that there is a retarded or inadequate production
of gonadotropic hormone by the anterior lobe in enucleated
rats.
There is not sufficient evidence as yet to determine whether
the influence of light upon the pituitary, via the retinal
components, is purely nervous, endocrine, or both. Le Gros
Clark, NcICeown and Zuckerman ( '39) showed that the normal
OPTIC ENUCLEATION IN THE MALE RAT
71
pituitary response to visual stimuli does occur in the absence
of the superior colliculi and in the blocking of all retinal
impulses to any part of the mid-brain, to the pretectal area,
to the dorsal nucleus of the lateral geniculate body, and to the
visual cortex. On the basis of this evidence they suggested
that visual responses of the pituitary depend on impulses
passing either to the ventral nucleus of the lateral geniculate
body, or to the subthalamus by way of the accessory optic
tracts.
It is also possible that there is a relationship between
retinal stimulation of the pituitary and visual purple and
vitamin A. Wald (’35) demonstrated that visual purple exposed t o light decomposes into retinene and finally, among
other products, vitamin A. Darkness causes a regeneration of
visual purple. Johnson (’39) reported that the retinene of
vitamin A deficient rats showed a progressive degeneration
of rod outer segments to the inner nuclear region as the
deficiency progressed. Sutton and Brief (’39) reported that
rats depleted of vitamin A had pituitaries with “greater
potencies ’’ than pituitaries of normal or castrated animals.
The analyses of vitamin A content of eyes, livers, etc., of
animals kept in constant light, constant dark etc., with a correlated analysis of pituitary potency would no doubt be
revealing.
It is entirely possible that the alternate breakdown and
regeneration of visual purple characteristic of normal diurnal
conditions is necessary to the optimal stimulation of a
balanced L.H. and F.S.H. production by the pituitary. From
the work previously cited it appears that female animals in
constant light tend to have prolonged oornified stages, with
a high concentration of ovarian follicles, and a pituitary
rich in F.S.H. Female animals in constant dark h a w a
normal vaginal cycle, or a cycle shorter than animals in
constant light, with heavy luteinization in the ovaries, pituitaries high in L.H. and a high storage of vitamin A in the
liver. Females in alternating light and dark have a pituitary
72
LEDVIG QUSTAV BROWMAN
with the normal balance between L.H. and F.S.H., and livers
with less vitamin A stored than the constant dark animals.
I n any case it seems reasonable to assume that the primary
process in the series of events which leads to stimulation of
gonadal activity by visible radiation is stimulation of the
retina, with the intermediate step the activation of the anterior
lobe of the pituitary. Removal of the eye (optic enucleation)
in the rat causes a marked delay in the various phenomena
characteristic of normal growth and sexual maturity.
8UMMARY
Rats from which both eyes were removed at birth weighed
consistently less throughout life than did their normal-eyed
litter mates (134 normal, 134 blind). Evidence indicated that
this weight difference was probably not due to the operation
per se or to lowered food consumption. Young at weaning
from bilateral enucleated females weighed less than did young
from normal litter mate females (200 animals).
Retardation in the development of the testes and seminal
vesicles in enucleated animals was apparent beginning at
ahout 35 to 40 days of age. Enucleated rats reached a stage
in spermatogenesis comparable to the 40-day normal male by
about 65 days of age. Secretory activity of the seminal
vesicles of the bilateral enucleated animals was also delayed
approximately 3 weeks. Bilateral enucleated males killed a t
intervals of 5 days up t o day 100 had lighter seminal vesicles,
testes, and pituitaries than did their normal-eyed litter mate
brothers.
The evidence therefore appears to indicate that the removal
of the eye retards growth and disturbs gonadal functions
because of the relationship of the eye to the anterior lobe
of the pituitary. Since rats raised in the dark, bilateral enucleated rats, and rats born microphthalmic all showed a delay
in growth and sexual maturity, it is probable that the impact
of visible radiation on the retina is necessary for the development of the various phenomena characteristic of normal
growth and sexual maturity.
OPTIC EPTUCLEATION I N THE MALE RAT
73
LITERATURE CITED
BISSONNETTE,
T. H. 1938 Influence of light on the hypophysis. Long-continued
“night lighting” on hypophysectomizcd female ferrets and those
with optic nerves cut. Endoerin., vol. 22, pp. 92-103.
BROWXAN,
L. G. 1937 Light in its relation to activity and estrous rhythms
in the albino rat. J. Exp. Zool., vol. 75, pp. 375-388.
1938 a Effect of bilateral optic enucleation on certain reproductive
phenomena in rats under various light conditions. Anat. Rec., vol. 72,
suppl. p. 122.
1938 b Effect of bilateral optic enueleation on body weights of rats
under various light conditions. Anat. Rec., vol. 72, suppl. p. 41.
FISKE,
V. M. 1939 Effects of light and darkness on the activity of the pituitary
of the rat. Proc. Soe. Esp. Biol. and Med., vol. 40, pp. 189-191.
JOHNSON,
M. L. 1939 The effect of vitamin A deficiency upon the retina of
the rat. J. Exp. Zool., vol. 81, pp. 67-89.
DE JONGH,8. E., AND L. A. VAN DER WOERD 1939 wird die Produktion oder
die Wirkung des gonadotropen Hormons durch das Licht gunstig
beeinflusst? Acta Brevia Neerlandica, Bd. 9, S. 153-155.
LE Gms CLARK,W. E., T. MCKEOWNAXD 9. ZGCKERMAN 1939 Visual pathways
concerned in gonadal stimulation in ferrets. Proc. Roy. Soc. London,
V O ~ . B 126, pp. 449-468.
LUCE-CLAUSEN,
E. M., AND E. F. BROWN1939a The use of isolated radiation
in experiments with the rat. 11. Effects of darkness, visible and infrared radiation on three succeeding generations of rats. ( a ) Growth and
storage of vitamin A. J. Nutrition, vol. 18, pp. 537-549.
1939 b The use of isolated radiation in experiments with the rat.
111. Effects of darkness, visible and infra-red radiation on three
succeeding generations of rats. (b) Reproduction. J. Nutrition, vol. 18,
pp. 551-562.
MOORE,C. R. 1936 Responses of immature rat testes to gonadotropic agents.
Am. J. Anat., vol. 59, pp. 63-88.
MOORE,C. R., W. HUGHESAND T. F. GALLAGHER 1930 Rat seminal vesicle
cytology as a testis hormone indicator and the prevention of castration
changes by testis extract injection. Am. J. Anat., vol. 45, pp, 109-136.
MOORE,
c. R., AND D. PRICE 1938 Some effects of testosterone and testosteronepropionate i n the rat. Anat. Rec., vol. 71, pp. 59-78.
SUTTON, T. S., AND B. J. BRIEF 1939 Physiological changes in the anterior
hypophysis of vitamin A-deficient rats. Endocrin., vol. 25, pp. 302-307.
WALD, G. 1935 Carotenoids and the visual cycle. J. Gen. Physiol., 1701. 19,
pp. 351-371.
PLATE 1
FXPLAPTATION OF FIGURES
1 Normal-eyed male 1067, 40 days old, testis. Magnification before reduction
X 85. Note size of tubules, and stages in spermatogenesis.
2 Bilateral enucleated male 1065, 40 days old, testis. Magnification before
reduction X 85.
3 Normal-eyed male 1050, 61 days old, testis. Magnification before reduetion
X 85.
4 Bilateral enucleated male 1012, 60 days old, testis. Magnification before
reduction X 85.
(All above reduced one-fifth off.)
74
OPTIC ENUCLEATION lh’ TlIE YALE R A T
LUDVIG GCYTAV BI2OW;XfAN
75
PLATE 2
EXPLAh7ATICN OF FIGURES
5 Xornial-eyed iiiale 1067, 40 clays old, srininal vesicle. Blogriificatioii beforc
rrdurtion X 490.
6 Bilateral enuelcated rnale 1U65, 40 days old, seminal vcsicle. Magnification
bcforc reduction X 490.
7 Kormal-eyrtl niale 1060, 61 days old, seiiii~~al
T c4clc. 1f;ignific~:ition before
reduction X 490.
8 Bilateral ciiuelcutrd nialr 1012, 60 r l a j s old, seminal vcsiclc. Magnification
beforr reduction X 490.
(All above reduced one-fifth off .)
PLATE 2
OPTIC ENUCLEATION IN THE MALE RAT
LUDVIG GUSTAV HROWMAN
77
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