360 INTERNAL SECRETION 



phism is absolutely excluded. But experience shows that there are 

 recognizable differences between the greater number of the cells 

 and tissues in the two sexes. Apart from the genital apparatus 

 and the organs associated with its functions, such as the mam- 

 mary glands, male and female individuals differ widely from 

 one another physically, as in the details of the skeleton, the dis- 

 tribution and the amount both of the adipose tissue and the hair, 

 the development of the larynx, &c. ; and these physical differences 

 are accompanied by equally marked psychic divergence. These 

 facts suggest the question : Are the somatic cells sexual in 

 character ? That is to say, are they formed from a male or female 

 primitive origin ? There is a second possibility, namely, that 

 the sexual differentiation of the somatic cells is secondary and 

 dependent upon the unisexual cells of generation, that is, upon 

 the reproductive glands. Both these hypotheses have their sup- 

 porters. 



A large number of authors, Tandler and Gross more par- 

 ticularly, have laid stress upon the fact that what are called the 

 secondary sexual characteristics are, in reality, only characteristics 

 of the species, that is to say, properties peculiar to a species or 

 an order of vertebrates and having no primary relationship with 

 the organs of generation. Thus the mammary glands are the out- 

 come of an agglomeration of sweat glands which, later, became 

 the engine of a different function and was included within the 

 sphere of influence of the organs of reproduction. The beard of 

 the anthropoid apes and of man was also originally a charac- 

 teristic of species, for the upper lip of the human fcetus is clothed 

 with a hirsute growth which attains equal development in both 

 sexes. The antlers of the cervida?, again, were originally specific 

 characteristics of unknown function, which afterwards acquired 

 a secondary relationship to sex. Tandler and Gross were able 

 to prove that in the fcetus of the roe-deer there is a primitive 

 antler trace, the appearance of which is exactly similar in both 

 sexes, the only difference being that in the case of the male 

 development is progressive, while in the female further develop- 

 ment takes place in very rare instances only. The formation of 

 the antlers of reindeer is identical in both sexes, and the develop- 

 ment of the antlers in the female is unaffected by castration. 



But this translation of the characteristics of sex into charac- 

 teristics of species merely postpones the solution of the problem ; 

 it does not supply any evidence in favour of either of the current 

 hypotheses. The characteristic signs of species are undoubtedly 

 foreshadowed in the embryo, but the direction of their subsequent 

 development must depend on one of two determining causes : 

 either thev already possess a tendency to develop in a certain 

 manner, that is to sav, thev have sex ; or their development is 

 modified and differentiated by the internal secretory activity of 

 a genital gland. Both are possible. If the secondary sex 



