576 THE PHYSIOLOGY OF REPRODUCTION 



Consequently the amount of mammary growth during the 

 gestation period of the multiparous animal is relatively less. 



The changes which take place in the human female and in 

 other animals during pregnancy are in a general way similar 

 to those occurring in the rabbit. In women after the second 

 month the breasts are said to offer a nodular sensation on palpa- 

 tion, this being due to the hypertrophy of the mammary alveoH. 

 The nipples also enlarge, and at the same time become more 

 erectile and pigmented, while the areola surmounting the nipple 

 becomes broader and pigmented also, in dark individuals being 

 often almost black. The hypertrophy of the sebaceous glands 

 in the areola results in the formation of the so-caUed glands of 

 Montgomery, which appear as small round elevations. As 

 already mentioned, during the later months of pregnancy the 

 thin yellowish fluid known as colostrum can generally be 

 expressed from the nipples. 



The mammary glands are said to undergo growth at puberty, 

 and there can be no doubt that a slight hypertrophy generally 

 takes place in connection with each period of prooestrum and 

 oestrus. These changes must be ascribed to ovarian influence, 

 which, as has already been shown, is probably responsible for the 

 changes which occur at such times in the other generative organs. 

 Professor J. P. HiU informs me that in certain Marsupials the 

 amount of mammary growth occurring at each ovulation period 

 is so marked as to render it difficult to distinguish such animals 

 from pregnant ones. Gellhorn ^ refers to a case of a woman 

 who had abnormal mammary glands with seven nipples in the 

 neighbourhood of the mons veneris, and who yielded milk at 

 each menstrual period. Other similar cases have been recorded. 

 This phenomenon is, of course, contrary to the more usual 

 tendency for menstruation to be in abeyance during lactation. 



The Factors which are concerned in the Process 

 OP Mammary Growth 



It has just been mentioned that the mammary glands in the 

 female, begin to undergo enlargement at the period of puberty 

 in correlation with the increase in ovarian activity. In Man 



1 Gellhorn, "Abnormal Mammary Secretion," Jour. Amer. Med. Assoc, 

 Nov. 21, 1908. 



