6o8 THE PHYSIOLOGY OF REPRODUCTION 



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 palpation, this being 

 due to the hypertrophy of the mammary alveoli. 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-called 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 proved, is responsible for the changes which occur at such times 

 in the other generative organs, while, as shown below, the mammary 

 growth which takes place after ovulation is due to the corpus luteum. 

 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 conceened in the Processes 

 OF Mammary Growth and Secretion 



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 the 

 difference between the glands in the two sexes is first manifested at 

 this time. The slight hypertrophy which occurs in connection with 

 each procestrous period has been referred to, while the great growth 

 which the glands undergo during pregnancy has also been described. 



It was formerly supposed that there was a direct reflex connection 

 between the growth of the mammary glands and the development 

 of the embryo in the uterus, the hypertrophy of the glands 

 being determined through the intermediation of the central nervous 



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

 21st November 1908. 



