Development of Mammary Glands in the Rabbit. 541 



before parturition, but does not occur in man and Dasyurus till several hours 

 after it, so that the secretion of milk does not coincide with the expulsion of 

 the foetus. We have observed a case of a goat in which milk was secreted in 

 large quantities (800 c.c. per day) for three weeks before the kids were born. 

 This goat was served on September 28 and aborted on November 6 ; it was 

 served again on November 20 and came into milk on April 1, the kids being 

 born on the 21st of that month. 



A further interesting fact which seems to be correlated with the diminished 

 activity of the corpus luteum is the instinct of nest making. Often at the 

 end of pseudo-pregnancy, at the time the animal is also " on heat," or a short 

 time after the removal of the ovaries or foetuses, fur is plucked out and a nest 

 is made in preparation for the expected young. 



The Corpus Luteum. 



The conclusion arrived at from the previous experiments was that the 

 growth changes of the mammary gland in the second half of pregnancy are 

 dependent on the foetus, but probably not directly. Since we know that 

 the presence of the foetus (in those animals which ovulate spontaneously) 

 causes the corpus luteum spurium to develop into the corpus luteum of 

 pregnancy, we should expect much the same thing to happen in the rabbit. 

 If it does so, we might expect that the further development of the mammary 

 gland is brought about as a result of the further growth of the corpus 

 luteum, for it seems more likely that the mammary gland should be con- 

 trolled from one point than from two, as Ancel and Bouin suggest. 



The supposition that the corpus luteum of the Eutheria remains in an 

 active state during the second half of pregnancy is not in accordance with 

 the commonly accepted views, but O'Donoghue* has shown that the whole 

 of the process of growth of the mammary gland and of milk secretion in the 

 marsupial cat {Dasyurus) is under the influence of the corpus luteum. 



He states that, in many cases after coitus where pregnancy did not 

 supervene, the growth and activity of the mammary glands reached a stage 

 of development indistinguishable from that which occurs in mammals a 

 few days after parturition. 



Sandesf also states that he found that the formation of the corpus luteum 

 in Dasyurus was rapid, and that it persisted during the greater part of the 

 time that the animal was lactating, and only disappeared when the young 

 animals became independent. 



* O'Donoghue, ' Quart. Journ. Mic. Sci.,' vol. 62 (1911). 



+ Sandes, ' Proc. Linn. Soc. New South Wales,' vol. 28 (1903). 



