ix THE SKIN AND CUTANEOUS GLANDS 517 



arrested . development or atrophy of the uterus ; Foges (1905) 

 showed by experiments on young rabbits and kittens, that the 

 development of the mammary gland is connected with the presence 

 of ovaries capable of functioning, while the presence or absence of 

 the uterus was immaterial. On the other hand, Pfister (1901) 

 observed a reflex influence of the mammary glands upon the 

 genital apparatus, excitation of the former causing secretion in 

 the genital organs, return of menstruation, and so on. 



All these investigations into the innervation of the mammary 

 gland await confirmation and development by further research. 



Eibbert (1898) made a number of experiments with the object 

 of investigating the development of the mammary gland during 

 pregnancy. 



According' to this author the development of the gland is not 

 controlled by the nervous system, because in a case of transplanta- 

 tion of a mamma from a virgin rabbit into a pregnant one, the 

 transplanted gland developed mammary functions. 



These results, according to most authors, prove definitely that 

 glandular development occurs by a chemical stimulus or hormone 

 carried in the blood. But it must be remembered that Eibbert 

 alone, and in one single case, obtained a positive result ; all the 

 control researches have so far proved negative. 



By another method Lane-Claypon and Starling arrived at a 

 theory in accordance with that of Eibbert, in which they not 

 only assume generally, with him, that the blood during pregnancy 

 contains the hormone or stimulating substance for the development 

 of the mammary gland, but claim to have located the origin of 

 this substance. They state that the foetus itself produces specific 

 hormones which stimulate the development of the mammary 

 gland. They find that repeated injections of extract from the 

 foetus (a large number, over 100, being employed) lead to develop- 

 ment of the mammary gland in virgin rabbits. C. Foa (1908) 

 repeated these experiments, using foetal extract from different 

 species, particularly bovine, and arrived at the same results. The 

 hormones which develop the mammary gland are not specific for 

 the species to which the foetus belongs; their action, as was 

 noted' by Camus, Gley (1902), and others, is similar to that of 

 the hormones of the pancreatic and enteric secretion (secretin}. 



We cannot, however, admit that these results have the decisive 

 importance attributed to them in favour of the theory of 

 chemical co-ordination. Even admitting that extract of foetus, 

 injected artificially in very large amounts, is able to activate the 

 development of the mammary gland, we are still far from any 

 direct proof that the foetus really gives off the supposed specific 

 hormones to the maternal blood, during physiological pregnancy. 



We have already pointed out (p. 90) in regard to the pancreatic 

 and intestinal secretions that the theory of secretin as a specific 



