578 THE PHYSIOLOGY OF REPRODUCTION 



Further evidence in support of the conclusion that the con- 

 nection between mammary and foetal growth is not nervous in 

 character is supphed by those experiments in which portions of 

 gland were successfully transplanted to abnormal positions in 

 the body. Thus in an experiment on a guinea-pig Ribbert ^ 

 grafted mammary tissue from the normal position to the neigh- 

 bourhood of one of the ears. Notwithstanding the fact that 

 the transplanted gland had lost its normal nervous connections, 

 it underwent enlargement during a subsequent pregnancy, and 

 afterwards secreted milk. Pfister ^ states that he performed 

 a similar experiment on a rabbit, and obtained a similar result. 



The inference is, therefore, that the relation between the 

 growth of the mammary glands and the development of the 

 foetus in the uterus is chemical in nature. 



As Miss Lane-Claypon and Starhng have pointed out, the 

 phenomenon of fertihsation succeeded by foetal growth involves 

 the occurrence of changes in the ovaries and in the uterus (both 

 in the muscle and in the mucous membrane), as well as the forma- 



vasomotor fibres for the vessels of the mammary gland, and that these affected 

 its secretory activity by controlling the blood supply. Mironow (" De 

 rinfluenoe du Systfeme Nerveux des G-landes Mammaires," Arch, dee Sciences 

 Biol, de St. Petersiourg , vol. iii., 1894) states that artificial stimulation 

 causes a reduction in the quantity of secretion. He states further that 

 whereas section of the external spermatic on one side has no effect on the 

 secretion, section on both sides diminishes it, but that the diminution only 

 comes on gradually after a number of days. After complete severance 

 of all the nerves in pregnant animals the glands may continue to grow and 

 yield milk after parturition. Basch {loc. cit.) states that extirpation of 

 the cseliac ganglion or transection of the spermatic nerve does, not inhibit 

 the secretory process, but increases the number of colostrum corpuscles. 

 There is abundant evidence of a general kind that the central nervous 

 system in some way exerts an influence on the mammary gland. Thus the 

 effects of nervous shock in altering or inhibiting milk secretion in women 

 are well known. Moreover, the occurrence of uterine contractions on putting 

 the child to the breast, and so stimulating the nipples, is evidence of a 

 nervous connection. It would seem probable, therefore, that though the 

 mammary gland is essentially an automatic organ, the connection of which with 

 the generative organs is through the vascular rather than the nervous system, 

 yet it is under the regulating control of the latter by means of secretory 

 or vasomotor fibres. 



^ Ribbert, "Ueber Transplantation von Ovarium, Hoden und Mamma," 

 Arch. f. Entvnck.-Mechanik, vol. vii., 1898. 



^ Pfister, " Ueber die reflektorischen Beziehungen zwischen Mammee und 

 Genitalia muliebria," Beitrdge zur Qeh. und Oynak., vol. v., 1901. 



