1906.] Growth and Activity of the Mammary Glands. 507 



bitch, thus severing all possible nervous connections between the pelvic 

 organs and the mammary glands. This clog gave birth to puppies at full 

 term. Pregnancy was attended with the normal hypertrophy of the mammary 

 glands, and the bitch successfully suckled one of the puppies. A similar 

 case has been recorded by Routh.* 



A woman when seven months pregnant was the subject of fracture of the spine at the 

 sixth dorsal vertebra, completely crushing the spinal cord at this level. Parturition 

 occurred two months later, and the woman was able to suckle the child normally. 



Moreover we have experimental evidence that the correlating mechanism 

 between the different parts of the generative system is not nervous. Thus 

 Knauerf showed that, whereas extirpation of both ovaries puts an end to the 

 periodical changes in the uterus which are responsible for the phenomena 

 of " heat," both ovaries can be transplanted, thus dividing all their nervous 

 connections, without undergoing complete atrophy and without abolishing the 

 phenomena of " heat." We must conclude therefore that the connecting 

 link in all these cases is chemical rather than nervous. It remains for us to 

 determine the origin of the exciting substance or substances, as well as their 

 mode of action. 



In the case of the mammary glands we have really two questions to decide. 

 We have to determine why the secretion of milk appears only at the end or 

 after the termination of pregnancy, and in the second place the origin of the 

 stimulus which, during pregnancy, is responsible for the hypertrophy of the 

 mammary glands. 



The Causation of the Secretion of Milk after Parturition. 

 In Man the secretion of milk commences two to three days after parturition. 

 During the greater part of pregnancy a fluid can be expressed from the 

 breasts, and this fluid can be obtained in greater quantity after birth ; it is 

 not true milk, but a watery fluid ricli in proteids, which is called colostrum. 

 In certain recorded cases where pregnant women have suckled during 

 pregnancy, the fluid that has been obtained has also not been true milk, but 

 of the nature of colostrum. In some animals, such as the rabbit, true milk 

 can be obtained from the glands during the last two days of pregnancy. In 

 each case, however, the factor which sets the secretory process going must be 

 the same, and the question at once arises whether the secretion is due to a 

 change in the metabolism of the uterus or ovaries, or to the absorption from 

 the involuting uterus of products which may act as a special stimulus to the 

 hypertrophied gland. 



* 'Obstetrical Society of London Trans.,' vol. 39, 1897. 

 t ' Archiv f. Gyniikol.,' p. 322, 1900, 



