THE GENERATIVE GLANDS 395 



gland. This gland not only exercises a protective influence, but 

 it determines the appearance of the somatic male characteristics. 



The behaviour of Leydig's cells during the embryonal period 

 and at other stages of existence points to the same conclusions. 

 The first appearance of Leydig's cells in the embryo precedes the 

 sexual differentiation of the primordial genital cells. The struc- 

 ture of the former indicates an exceptional degree of activity 

 during embryonal life. Bouin and Ancel thought it possible that 

 it is these cells which, by means of their specific internal secretion, 

 determine the sex of the generative cells that it is their influence 

 upon the indifferent primitive genital trace which causes the latter 

 to take on the male aspect. 



The sex of the somatic cells and, in consequence, the develop- 

 ment of the secondary genital organs and the further development 

 of all the male characteristics present at birth, are, then, de- 

 pendent upon the interstitial cells of Leydig. The normal 

 development of the secondary characteristics in the course of 

 post-uterine existence can only be ascribed to the function of this 

 tissue. From birth to about the beginning of puberty at a time, 

 that is to say, when somatic sexual divergence is least clearly 

 marked the' interstitial gland shows the minimum relative 

 development. 



In quite young animals, ligature of the vas deferens does 

 not at first inhibit spermatogenesis (Griffiths), and the results of 

 the operation are first observed as secondary consequences at the 

 period of puberty, when formation of semen normally takes place. 

 Inhibition of development of the interstitial gland in early youth 

 leads to arrest of the development of the secondary sex charac- 

 teristics. In the course of their experiments with rabbits, Bouin 

 and Ancel observed certain animals which, after ligature of the 

 spermatic cord at the age of 7 to 8 weeks, developed the habit 

 and behaviour of castrated animals. Microscopic examination of 

 the testicle showed atrophy, not of the generative part only, but 

 also of the cells of Leydig. These cells were few in number, they 

 appeared reduced in size, and showed no cytological signs of 

 secretory activity; they contained a large quantity of pigment 

 granules. These investigators nre of the opinion that the differ- 

 ence in the condition of animals after ligature of the vas deferens 

 in early youth is dependent upon whether the excretory duct 

 only of the testicle is ligatured or whether the nerves which supply 

 the testicle are also included. Resection of the nerves contained 

 in the spermatic cord, without ligature of the vas deferens, may 

 lead to atrophy of the cells of Leydig. If the spermatic duct only 

 is ligatured, or if the resected nerve-fibres grow together again, 

 the lesion of the internal secretory tissue elements is either very 

 slight or is quite transitory. S. Vincent and Copeman also found 

 that complete suppression of both the internal and external secre- 

 tion of the testicle is only to be effected by the ligature of the 



