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THE RELATION BETWEEN THE CORPUS LUTEUM
AND THE MAMMARY GLAND.
BY G. DRUMMOND-ROBINSON AND S. A. ASDELL.
(From the Animal Nutrition Institute, School of Agriculture,
Cambridge.)
INTRODUCTION.
IT is generally accepted that the stimulus for the normal development
of the mammary gland is derived from the corpus luteum, the stimulus
being hormonic in^ nature.^ The^ question whether the^ foetus has^ any
influence upon the mammary development during pregnancy, apart
from that which it^ exerts^ by prolonging the life of the corpus luteum,
is, however, still undecided. In view of the intimate connection between
this organ and foetal implantation and nutrition, any attempt to solve
the problem by removing the corpus luteum, while still retaining the
live foetus, seems for the present, out of the question. Loeb and Hes-
selberg(l) removed^ the^ corpora lutea in^ pregnant guinea-pigs at from
3-6 days after copulation. They state that in some cases an examination
at from (^) 14-181 days after coitus showed that abortion had not taken
place, and^ that^ a^ new^ ovulation, with^ consequent production of new
corpora lutea, had not occurred. It is difficult to reconcile this with their
observation that the presence of a corpus luteum is necessary for the
production of the decidua, and with Fraenkel's(2) statement that, in
the rabbit, removal of the corpora lutea in the early stages of pregnancy
is always followed (^) by abortion. Loeb and (^) Hesselberg found in the
guinea-pig that, whether abortion took place or not, proliferation of the
mammary cells, manifested^ by the^ presence of mitotic figures, was not
taking place at the time of examination. In their control guinea-pigs
at this stage, of seven cases the mammary cells are described as pro-
liferating in three and as intermediate in four. (^) Proliferation is not then a constant feature of this (^) early stage of pregnancy in this species. Fur-
thermore, associated with the cyclical corpus luteum of cestrus, there
is a considerable development of ducts before pregnancy occurs, and
the corpus luteum of pregnancy does not appear to (^) stimulate the mammary gland to further growth (^) immediately. The alveolar growth
CORPUS (^) LUTEUM AND MAMMARY GLAND
seems to be started (^) by the action of the corpus luteum of (^) pregnancy- after some retrogression due to the cessation of the stimulus from (^) the
previous corpus luteum of cestrus has been made good-at about the
time that the cyclical corpus luteum would have (^) degenerated. In the work on the goat described in this (^) paper, no light is thrown on the (^) question as to whether (^) mammary development may occur in the absence of the corpus luteum if (^) the foetus is (^) present, for in all (^) cases except one, abortion followed the removal of the (^) corpora lutea. In (^) the
single case which proceeded to term, a small corpus luteum was found
near the hilum of the (^) ovary, in which position it had (^) apparently been overlooked at the time of the (^) operation.
Woodman and Hammond(3) have shown that in the cow, pregnant
for the first time, a cloudy secretion with the consistency of honey is
to be obtained from the (^) udder from about the twentieth week of preg- nancy (^) onwards. (The duration of (^) pregnancy in the cow is about (^40)
weeks.) Asdell(4) confirmed this, and demonstrated the relation of this
fluid (^) to colostrum and to milk, (^) colostrum being shown to consist of (^) a
mixture of the viscous secretion, often containing up to 38 p.c. of
globulin, with milk. The abrupt appearance of this globulin secretion
at half-way through pregnancy was shown to occur in the goat also. In
this species it (^) appeared at the tenth week of (^) the 21 weeks' pregnancy.
This period is known to be (^) that at which the growth of (^) the alveoli, as
distinct from that of the ducts, begins. Hammond and Sanders(5)
have (^) shown that, at this stage in pregnancy, the yield of (^) the lactating
cow shows a distinct fall which is continued until the cow is dry, usually
about (^8) weeks before (^) parturition. This would appear to be (^) due to the
entry of (^) many of the mammary cells upon (^) a growth phase. It is there-
fore related to the phenomena already described.
In this (^) paper the relation between the (^) corpus luteum, the globulin
secretion, and milk (^) secretion is considered. The (^) method adopted has
been to remove the corpora lutea or the whole ovary from goats pregnant
for the first time. In some cases the operation has been performed about
(^2) weeks before the globulin secretion was due, in others, (^2) weeks after
it had appeared. (^) The subsequent mammary reactions have been studied
and reported.
Experimental. The modern goat in the (^) hands of the pedigree breeder shows (^) a strong tendency to lactate (^) in the absence of pregnancy (^) (Asdell(4)). The goats
in which this phenomenon occurs are nearly always found to be animals
with that blend of blood-a (^) blend of English, Nubian and (^) Swiss-which
PH. LXI. (^40)
CORPUS LUTEUM AND MAMMARY GLAND.
out, the cavity being scraped with a sharp spoon and cauterised. The
corpora lutea shelled out readily, leaving a smooth lined cavity. It was
found to be difficult to discover all the corpora lutea as they were un-
pigmented and were sometimes hidden near the hilum of the (^) ovary. If
a follicle were pricked during the operation, the cavity was cauterised.
A summary of the operations and their consequences is given in
Table I. Discussion. From these experiments it is evident that the (^) appearance of milk
in quantity after the removal of the corpora lutea was always preceded
by the appearance of the viscous globulin secretion. The case of goat 7
is of great importance in this respect. It is the only case of a considerable
number examined in which the globulin secretion had not appeared by
the eleventh week of pregnancy. In this goat, although the corpora lutea
were removed at the thirteenth week, no milk was secreted. This ex-
ception supports the inference drawn from the other experiments that
milk (^) secretion in quantity does not occur unless the (^) mammary gland
has passed through a stage of development which is characterised by
the production of globulin. It is also shown that the (^) growth of the alveoli is always in progress when the thick secretion has appeared. In view of the fact that the globulin secretion appeared whether the corpora lutea had been removed or not, in some of the goats (^) operated
on early in pregnancy, it was decided to remove the whole ovary in
some cases at this period. Unfortunately, circumstances arose which
prevented the use of more than two goats for this purpose. Of these,
one (^) died after the operation, but the (^) other, goat 8, gave a well-defined positive result. (^) The viscous secretion, demonstrated to be (^) largely globulin, appeared 17 days after the operation, about the normal time for the (^) appearance of the secretion. This suggests that, the (^) stimulus for (^) mammary growth having been given, the (^) gland can continue deve- loping for a time. Either (^) sufficient hormone is stored in the system, or the (^) impetus already imparted to the cells is (^) sufficient for a while. The latter seems the (^) more satisfactory explanation, for it is unlikely that the hormone would remain stored (^) and potent for over a fortnight. There is (^) the possibility that a dead foetus may have been lying in the uterus and have caused this (^) development. This, however, is unlikely, since in goat 3 such a possibility is (^) excluded, while in goat 4 the involution of the (^) uterus was such that abortion of the (^) foetus had apparently taken
place a few days after the operation. (^) This development which occurs in the absence of the corpus luteum is not followed by milk secretion.
612 G. DRUMMOND-ROBINSON AND S. A. ASDELL.
Further evidence of the importance of the half-way stage in mammary
growth is given by Hoop er(6), who has considered the effect of abortion
at different stages of pregnancy on the milk yield of the lactating cow.
In six cases in which abortion occurred in the interval between the
103rd and the 183rd day of pregnancy, i.e. up to a month after the
globulin secretion^ would have^ appeared in a prima gravida, the average
milk secretion for the month (^) preceding the abortion was (^516) lbs., and for the month following 524 lbs. In the second (^) group of six cases (^) abortion
occurred from 216 to 254 days after conception. The average duration
of pregnancy in the cow is about 285 days. In this group the average
yield rose from 411 lbs. to 683 lbs. In the earlier (^) set, the rise is of (^8) lbs.
only during the month, while in the later abortions, where mammary
growth has set (^) in, the rise is 272 lbs.
Another point which has emerged from this work is that after the
removal of the corpora lutea, ovulation is spontaneous, occurring from
the sixth day onwards. There are two cases of actual ovulation after
operation in these goats, but the signs of cestrus were vague. The spon-
taneity or^ otherwise of ovulation in the goat does not seem to have been
determined previously, but in view of the cyclical cestrus during the
breeding season, it is probable that ovulation always is spontaneous. In
order to test this point, a goat was killed 80 hours after cestrus was
first observed. Ovulation had occurred, and a corpus (^) luteum was found in each ovary. There was no possibility of (^) coitus having taken place. The case of delayed appearance of the globulin (^) secretion in goat 7 is of considerable (^) interest for it denotes a delay in the development of
the mammary gland. This was confirmed by histological examination.
Development was less at 14 weeks than is usual at 10 weeks. Removal
of the corpora lutea in this animal did not result in the (^) production of milk as was the rule in goats (^) operated on at this time or a week earlier. This indicates a (^) lack of co-ordination between the corpus luteum (^) and the mammary gland. It is (^) possible that this lack of co-ordination is the result of the action of some unknown inherited tendency. If so, it (^) would furnish an explan-ation of the (^) action of such genetic factors as are known to affect the (^) milk yield, for the degree of development attained by the gland must determine the maximum yield (^) of milk at the commencement of lactation. In a paper on the decline of milk yield with the (^) advance of pregnancy,
Gaines and Davidson(7) state that this decline is probably due to an
inhibiting hormone which is said to circulate in the blood of the (^) pregnant
animal, and that this inhibition is removed at parturition. They consider
614 G. DRUMMOND-ROBINSON AND S. A. ASDELL.
REFERENCES.
- Loeb and Hesselberg. Journ. Exp. Med. 25. p. 305. 1917.
- Fraenkel. Arch. fur Gyn. 68. (^) p. 438. 1903.
- Woodman and Hammond. Joum. Agric. Sci. 8. (^) p. 180. 1923.
- Asdell. Ibid. 15. p. 358. 1925.
- Hammond and Sanders. Ibid. 8. p. 74. 1923.
- H ooper. Kentucky Agric. Exp. Sta., Bull. 248. 1923.
- Gaines and Davidson. Amer. Joum. Physiol. 9. p. 325. 1926.
