INTERNAL SFXREtlONS gt 



the development of the erectile structures about the head (comb, 

 wattles, etc.). The general plumage, on the other hand, is as 

 characteristically male in the capon as in the cock, and the 

 spurs also are unaffected. So also the castrated drake ditt'ers 

 only slightly from the uncastrated male bird (Goodale, Pezard). 



AVith the frog, castration inhibits the development of the 

 clasping pad at the base of the forefinger at the breeding season, 

 as well as the associated hypertrophy of the musculature of the 

 fore limb. A¥ith other amphibians and also with fishes, the 

 appearance of certain secondary male characters has been shown 

 to be correlated either with the testis or with a special organ 

 usually in contiguity with the testis. With all the higher verte- 

 brates, however (birds and mammals), it is abundantly evident 

 that the secondary sexual characters in the male are dependent 

 upon the presence, and consequently upon the functional activity, 

 of the testis itself. 



The Internal Secretion oe the Testis 



The idea that the testis exerted its influence upon the secondary 

 sexual characters or upon the metabolism through an internal 

 secretion discharged into the blood rather than through the 

 intermediation of the nervous system, seems to have been first 

 postulated by Bordeu, who was Court Physician to Louis XV. of 

 France in the eighteenth century. It was not, however, until 

 1849 that the conception came to be based upon definite scientific 

 evidence, for it was in that year Berthold published the results 

 of his experiments upon testicular transplantation in fowls. 

 Berthold's views and work were for many years lost sight of, but 

 it is remarkable to note that some of the strongest and clearest 

 evidence that the testis elaborates one or more chemical products 

 which are secreted internally and carried through the circulation, 

 is that derived from experiments with testicular grafts, carried 

 out in a manner essentially similar to that employed by Berthold. 

 That the gonad (whether male or female) when removed from the 

 normal position and transplanted on to an abnormal position 

 (such as the ventral peritoneum), where it no longer possesses 

 its ordinary nerve connections, yet still retains its usual influence 

 on the secondary sexual characters and even upon the accessory 

 sexual glands, is only explicable on the assumption that it secretes 



