Download the influence of age at castration on the size of various organs

THE INFLUENCE OF AGE AT CASTRATION ON
THE SIZE OF VARIOUS ORGANS
BY JOHN R. BAKER.
From the Department of Zoology and Comparative Anatomy, Oxford.
(Received $th February 1927.)
(With Three Text-figures.)
INTRODUCTION.
IT has been known for a long time that the effects of castration are more marked
if the operation is performed early than If It Is performed late. It was the object
of the experiment described below to pet this fact upon a quantitative basis.
I wish to thank Dr R. A. Fisher for most kindly explaining to me how to deal
statistically with small samples, and Mr F. C. Sherlock for skilful practical assistance. Mr W. Hanson kindly arranged for his pigs to be castrated by a veterinary
surgeon at the appropriate ages, and Messrs Marsh and Baxter cooperated In
killing some of them and removing the necessary organs.
METHOD.
The experiment was carried out upon 17 male Large White pigs. Pigs were
chosen because their large size enabled the small organs such as the pineal and
pituitary to be weighed accurately. A pedigree Large White boar was the father
of all the pigs Investigated. Their mothers were two Large White sows, not of
pedigree stock. One of them was a daughter of the other, by the same boar that
was the father of all the experimental animals. These facts are mentioned to show
that the experimental animals were all closely related and unlikely to differ much
In their Inheritance as regards the size of the organs studied.
Six pigs were castrated at approximately 50 days, seven at 100 days, and two
at 200 days, while two were left uncastrated. In most farrows some pigs were
castrated at-one age and some at another, so as to discount differences In size of
organs due to environment rather than age at castration.
All the pigs were killed at approximately 300 days from birth, and the weight
of each noted. The weight was obtained as follows (or In a very similar way).
When the pig had been stuck with a knife, the escaping blood was caught In a
bucket and weighed. This weight was added to the weight of the body, which
was taken Immediately afterwards on a spring balance. From the total weight
thus obtained was subtracted the weight of the large Intestine with Its contents.
(It was not thought necessary to weigh the contents separately, since the weight
of the large Intestine without the contents Is small.) There was little food In the small
Intestine since the pigs were starved for a day before death, and for the same
reason the contents of the stomach were usually small, but were weighed and
188
J O H N R.
BAKER
subtracted from the body-weight if not negligible. 0-5 kg. was subtracted for the
weight of urine If the bladder was distended to the usual extent; otherwise the
urine was weighed. The figure beyond the decimal point in the net weight expressed In kilograms Is not dependable.
As soon as possible after death, the following organs were removed and placed
in stoppered glass bottles: veslculae seminales, bulbo-urethrals (= Cowper's
glands), adrenals, thyroid, pineal, and pituitary. These organs were then removed
to the laboratory;, dissected free from fat and loose connective tissue, and weighed.
A certain amount of error must necessarily have been caused by evaporation. The
first four were weighed to the nearest 5 milligrams (or more accurately), the last
two to the nearest milligram. For purposes of comparison the weights were multiplied by 1000 (to avoid decimals to some extent) and expressed as percentages of
the net body-weight.
The whole of the results obtained In this Investigation are given In the Appendix1.
The first column gives the serial number of each pig. The second column Indicates
to which farrow each pig belongs. All the pigs designated by the same letter were
born In the same farrow. The remaining columns are sufficiently explained by
their headings.
In order to present the figures given In the Appendix In a way In which they
could be appreciated, the mean weights (x 1000, as percentage of body-weight)
of all the organs mentioned above of all the pigs castrated at each age were calculated for comparison with one another and with the mean weights of the same
organs of the uncastrated pigs.
The ordinary method of testing the significance of the differences between
means, consisting In the calculation of the Probable Errors of the means, Is not
really applicable to small samples such as those with which I had to deal. The
following method was therefore employed to test the significance of the difference
between two means.
The Standard Error was calculated in each case from the following formula,
the sums of the squares of the deviations from both means being lumped together:
/7i
i\ /
S.E. = J
- +T
nJ
bj\
V \a
where a and h are the number of Individuals castrated at each age, d Is the deviation
of each weight from the mean weight of Its group, and n = a + b — 2.
The difference between the means (or the difference between the mean of one
group and the single observation constituting the other group) was then divided
by the S.E., and a figure i obtained.
To find whether t was sufficiently large to be significant, reference was made
to the table of / given in Fisher's work on statistical methods (192s), where the
lowest significant value of t for each value of n is given. In this table various grades
of probability are tabulated; but only the P = -05 column was used, since this is
accepted as a test of significance.
1
The blanks in the Appendix are chiefly caused by the carelessness of butchers in failing to
keep the organs of different pigs separate.
Influence of Age at Castration on the Size of Various Organs 189
RESULTS.
The results are shown in full in the Appendix and graphically in Figs, 1 and 2.
Table I is an abridgment of the Appendix.
In the graphs the mean weight of each organ at 300 days (expressed as a proportion of the body-weight) is plotted against age at castration. In Fig. 1 the
ordinate is on a much smaller scale than in Fig. 2, so as to include the relatively
huge weights of the vesicuiae seminales and bulbo-urethrals in uncastrated pigs.
The weights of the organs of the uncastrated pigs are plotted as though these pigs
had been castrated on the day of death (approximately 300 days).
20
400r
Thyroid (x 1000)
Vesicuiae seminales
1
(xrooo) /
I
3
300
15
o
Bulbo-urethrals (x 1000)
Si
ao
3
«*
|
200
m es
5*
0
Vesicuiae semimks
1
(xiooo)
/ . Adrenals (x IOOO)
Pineal (xlOOjOOO)
10
Bulbourethrals
100
Pituitary (xio,ooo)
0
JS
I
CO
g
100
200 Not castrated
Age at castration (days)
(equivalent to.
castration at 300 days
Fig. 1.
=age at death)
TOO
200
Age at castration (days)
Fig. 2.
Table I.
Age at
castration
(days)
So
100
200
Not
castrated
Mean
bodyweights
(kg.) at
300 days
97-2
85-5
85
89
Mean weights at 300 days ( x 1000, as percentage of body-weight)
Vesicuiae
seminales
Bulbourethrals
Adrenals
2*69
1-52
4-55
5-58
1-76
3-.58
Significant Significant Significant
8-25
IO'I
I4-4
Significant Significant
132
356
Thyroid
Pineal
Pituitary
14-3
H'9
0-068
0-078
0-35
Q-45
18-9
0-080
0-42
Taken by themselves, these graphs are not very helpful, for they show only
the means and not the range of variation in each case. For instance* it is not
possible to determine by examination of Fig. 2 whether pigs which have been
castrated at 100 days have significantly smaller thyroids than those which have
190
J O H N R.
BAKER
been castrated at 50 or 200 days. To remedy this I have written the word "significant" between the comparable figures in the table, to indicate those cases in
which it was age at castration, and not chance alone, that determined the differences.
The significance of the differences between means was calculated as explained
under the heading "Method."
Each organ will now be considered separately.
Vesiculae seminales. It is well known that the vesiculae are small in castrated
mammals. Figs. 1 and 2 show graphically the effect of castration at different ages.
It will be noted that it makes little, or possibly no, difference whether the pig
be castrated at 50 or 100 days, the difference between the means not being statistically significant; but when castration is delayed to 200 days the difference in size
is very greats for the glands are about four and a half times as heavy. In uncastrated pigs the vesiculae are more than two hundred times as large as in those
which have been castrated at 50 or 100 days. We must conclude that the influence
of the testes upon the vesiculae is felt chiefly, or perhaps entirely, after the age of
100 days; and that the effect is very much greater between 200 and 300 days than
between 100 and 200 days.
Bulbo-urethrals. Nagel (quoted by Marshall (1922)) states that these glands
are of normal dimensions in castrated men, but Schneidemiihl (also quoted by
Marshall) records atrophy after castration in other mammals. In pigs I find that
castration has a very marked effect. If castration is deferred.to 200 days the bulbourethral glands grow much larger than they do in pigs which have been castrated
at 50 or 100 days. In uncastrated pigs they are very much larger, though the
difference is not so great as in the case of the vesiculae seminales (Figs. 1 and 2).
Adrenals. It has been stated by Paton (1913) that the adrenal cortex tends to enlarge
after castration. My experiments (which deal only with the gland as a whole)
show on the contrary that pigs castrated at 100 days have smaller adrenals than
those castrated at 200 days. When the mean for all pigs castrated at 100 days is
compared with the figure for the single individual castrated at 201 days, the value
of t is found to be 2-55, significance being reached at 2-447. The difference between
pigs castrated at 50 and 100 days is not significant, but might become so with
larger samples (Fig. 2).
Thyroid. The figures for the thyroid indicate that it makes little or no difference
when the animal is castrated, though this organ varies in size far more than the
others. A most interesting fact however emerges, namely that all the male pigs
born in the same farrow tend to have thyroids of about the same size, while the
different farrows differ markedly from one another in this respect. This is clearly
shown in Fig. 3, in which pigs born in the same farrow are bracketed together
irrespective of age at castration. Environmental influences are evidently important
in determining the size of this organ.
Pineal. From my experiments it appears that in pigs time of castration has no
effect upon the size to which the pineal grows, though Biach and Hulles (quoted
by Marshall (1922)) record atrophy of the pineal after castration in kittens. An
interesting point with regard to the pineal is that it tends to grow to a certain size
Influence of Age at Castration on the Size of Various Organs
191
(the mean of all individuals studied is 0-062 gm.) irrespectively of the size to which
the body grows. Thus a small pig has a relatively large pineal while a large pig
has a relatively small one. This can be expressed mathematically by finding (a) the
standard deviation from the mean of the actual weights and (b) the standard deviation from the mean of the weights expressed as percentages of the body-weight.
The figures for (a) and (b) are 21 and 32 per cent, respectively. One would of
course have supposed that (a) would have been much larger than (b).
Pituitary. Tandler and Gross, Fichera, Cimorini, and Sehonberg and Sakaguchi
(quoted by Marshall (1922) and Lipschiitz (1924)) record increase in size of the
pituitary after castration in rabbits, cattle, buffaloes, dogs and men, while Livingston
(quoted by Marshall) finds no effect in rabbits. My findings indicate that in pigs
castration has little or no effect upon the growth of the pituitary.
25
4>
§
20
u o
ft m
es os
§1
15 —
O a
X
4
53
10
£
Fig. 3.
Body-weight. There is considerable variation in body-weight, and, not unnaturally, a tendency for all pigs born in the same farrow to approximate more
closely to one another in weight than to pigs born in other farrows. Since in most
farrows some pigs were castrated at one age and some at another, this fact does
not render it impossible to note the effect of early and late castration on weight.
From the figures given in Table I it will be noted that the heaviest pigs are those
which were castrated at 50 days; but the means are not statistically different.
CONDITIONS IN THE ADULT UNCASTRATED MALE.
An uncastrated male pig (the father of all the experimental animals) was killed
at the age of several years for purposes of comparison. His body-weight was
241 kg. The relative weights of his organs are shown in Table II, which should
be compared with Table I.
It will be observed that the vesiculae seminales and bulbo-urethrals are smaller
192
J O H N R.
BAKER
in this boar, relatively to the body, than those of an uncasttated pig 300 days old.
In other words, the body grows faster than these organs after 300 days. The same
seems to apply to the adrenals.
The head and neck had unfortunately to be sold, so there are no figures for
the thyroid, pineal, and pituitary.
Table II.
Weights (x 1000, as percentage of body-weight)
Vesiculae
seminales
Bulbourethrals
Adrenals
197
85 +
5-06
DISCUSSION.
The experiment described above shows that the testes exert a very marked
influence on the vesiculae seminales and bulbo-urethrals between the ages of 100
and 200 days, and have also a significant effect upon the adrenals during this
period* Between 50 and 100 days, on the contrary, the effect is slight if there is
any at all. (The differences between the means are not significant statistically,
but since they are all in the same direction as the differences between the 100-day
and 200-day means, they might well become significant with larger samples.)
There are two conceivable explanations of this fact: after 100 days, either the
testes pour out a larger amount of hormone into the blood-stream or the glands
respond more readily to the hormone. From histological considerations I
regard the second alternative as the more probable. If the gonad hormone
suddenly began to be poured out at a certain time during development, one would
expect marked differences between the condition of the interstitial cells of the
testes before and after that time; for there is a great deal of evidence that the
hormone is secreted by these cells. That there are no such differences was shown
by Ancel and Bourn in their well-known researches (1903) on the interstitial cells
in the testes of the pig. These authors write: "Les cellules interstitielles du verrat
offrent les memes caracteres cytologiques que celles de 1'animal jeune." This
fact is clear from their figures. Figs. 5 and 7 in their paper, showing the structure
of the interstitial cell in the suckling or slightly older pig, should be compared with
Fig. 17, showing the adult condition. In both cases the interstitial cells are loaded
with secretory products. Further, these cells are abundant at all stages.
These considerations show that Steinach's term "puberty gland," as a synonym
for the interstitial gland of the testis, is rather misleading. They give some
support to Crew's hypothesis (1921) of intersexuality in goats and pigs. Crew
supposes that there is a more or less definite time in the development of each
accessory organ, during which it is capable of being stimulated to develop by the
testicular or ovarian hormone, while before or after this time no amount of gonad
hormone will affect it. The investigations described in this paper, taken in con-
Influence of Age at Castration on the Size of Various Organs 193
junction with Ancel and Benin's histological results, seem to show that there is at
any rate a time before which the hormone (though present) has little or no effect,
and that the accessory sexual organs become progressively more and more capable
of responding to it. It is apparently at about the age of 100 days that the vesicuke
seminales and bulbo-urethrals begin to respond in the pig, and between 200 and
300 days their response is very much greater than it was between 100 and 200 days.
Careful examination of the figures given in the Appendix reveals the fact that
in each castration-age-group, the pigs which have large vesicuke seminales tend
to have large bulbo-urethrals and those with small vesicuke tend to have small
bulbo-urethrals. Previous considerations rule out the possibility that the correlated
size of these organs is to be accounted for by early or late outpouring of the testishormone. The amount of testicular hormone poured out (before castration) can
hardly be the cause, for it is well known from experiments that a portion of
testicular substance only one-fiftieth the size of two normal testes suffices in
mammals for full development of the accessory sexual organs. It is not a case of
heterogony, for it is not simply the large pigs that have these organs highly developed. The case is similar to what everyone knows to be the case in men; namely
that some have secondary sexual characters more developed than others. It appears
to me possible that the potency of the sex-chromosomes may vary and affect the
size to which the accessory organs grow, just as we have good reason to suppose
that the sex-chromosomes of insects vary in potency and affect the degree of development of the sexual organs; though there is5 of course, this difference, that in
mammals the accessory organs cannot develop save in the presence of the testicular
hormone. (This explanation would of course not cover "eunuchoid" individuals,
for here the small size of the accessory sexual organs is undoubtedly caused by the
very small size of the testes.) This hypothesis would be rendered the more likely,
if it could be shown that the size of these organs is not determined by general
metabolic conditions.
SUMMARY.
Male pigs were castrated at the ages of 50, 100 and 200 days. Others were not
castrated. All were killed at 300 days. The weights of various sexual and endocrine
organs at 300 days were determined, and a comparison instituted between pigs
castrated at each age. The following results were obtained:
(1) The vesicuke seminales, bulbo-urethrals, and adrenals are smaller when
castration is performed at 100 days than when it is performed at 200 days. There
is much less difference (possibly none) according to whether castration is performed at 50 or 100 days. In uncastrated pigs the vesicuke seminales and bulbourethrals are enormously larger even than those of pigs castrated as late as 200 days.
(2) It is probable that some change occurs in these organs at about the age
of 100 days, rendering them progressively more and more sensitive to the gonad
hormone.
BjEB*viii
f
3
194
JOHN R. BAKER
(3) The thyroid,, pineal, and pituitary are not significantly affected by time of
castration. Body-weight also is not significantly affected.
A general discussion is given on the causes governing the size of the accessory
sexual characters in mammals.
REFERENCES.
ANCEL, P. and BOUIN, P. (1903). Arch, de Zool. Exp. Ser. 1, 4, 437.
CREW, F. A. E. (1921). Proc. Roy. Soc. B, 95, 90.
FISHER, R. A. (1925). Statistical Methods for Research Workers. (Oliver and Boyd, Edinburgh.)
LIPSCHUTZ, A. (1924). The Internal Secretions of the Sex Glands. (Heffer, Cambridge.)
MARSHALL, F. H. A. (1922). The Physiology of Reproduction. (Longmans, Green and Co., London.)
PATON, N. (1913). Regulators of Metabolism. (Macmiiian, London.)
APPENDIX.
Vesiculae
seminales
at
th
ys)
1-24
80
1-46
89-5
1-50
127
I-8I
105-5
105-5
1-48
1-41
I-I6
I-IO
2
97-2
1-44
1-52
1
0
0
0
0
91-8
1-67
86-3
1-32
i-55
i'33
1-82
i-53
2-49
173
2-05
O3
O3
3
3
03
75-5
62-2
77
83.5
92
106
171
1-40
1-22
i'53
1-76
01
85-5
i-46
1
02
71-4
509
13
1
0a
02
2
Thyroid
Adrenals
Pineal
Pit
Bodyweight
Weights
Weights
Weights
Weights
Weights
X
IOOO
X IOOO
X IOOO
X
IOOO
X
IOOO
Actual
at death Actual
Actual
Actual
Actual
Actual
weights as % of weights as % of weights as % of weights as % of weights as % of weights
(kg.)
(gm.)
body(gm.)
body(gm.)
body(gm.)
body(gm.)
body(gm.)
weights
weights
weights
weights
weights
1-65
1-83
i-68
i-43
1
0
0
Bulbo-urethrals
99
85
9-0
1-15
7-13
13
10*1
2-07
3'34
2-57
3-04
2-61
1-58
2-53
3-06
2-IO
2- S 8
378
5-04
2-31
i-77
2-95
9-19
2-48
.—
,—_
478
4-94
5-27
1-50
4-19
2-69
4-79
_
_—
5*35
3-89
4-99
3'97
4-55
3'34
2-44
4-15
4-64
4-11 +
4-47 +
5-06
476 +
7-18 +
2-74
4-17
2-87
2-40
4-91
6-04
2-52
1-67
3-58
12-9
16
16
12-6
14-4
89-5
281
314
90
101
88-s
353
317
399
356
144
117
163
132
89
18-6
6-i
9-2
7-0
0-075
0-050
0-050
0-062
0-061
0-088
0-099
0-062
0-056
0-049
0-058
0-083
0-30
0-31
0-40
0-33
14-8
0-064
0-068
0-33
17-5
19-0
13-2
—
15-3
0-057
0-057
0-135
0-097
0-066
0-47
0-37
0-32
0-34
8-8
6-9
11-9
0-052
0-049
0-084
0-075
0*055
0-048
0-058
0-052
0-055
0-25
.—.
0-060
0-078
0-37
18-9
0-057
—
0-080
—_
0-30
—
18-9
0-057
0-080
0-30
_
.—
"—*
.—~
.—
—
14-0
187
19-1
7-8
9-7
7-4
12-8
23-4
21-3
—
S-i6
671
8-3
io-8
4-47
4-28
s.6s
4-68
5 '3 5
4-66
5-33
5-58
9-1
8-i
10-9
5-89
8-25
5-89
8-25
7-4
10-6
13.5
.—
13-5
o-33
0-31
0-47
___
___
—
_—
_
.—
_