iv THE GENEKATIVE SYSTEM OF THE MALE 157 



of the epiphysis takes place after the first year of life ; in bullocks, 

 ossification is not complete till the fourth year. 



As with the secretions of the thyroid gland and supra-renal 

 capsules, Loewy (1903) has also tried the experiment of feeding 

 young fowl and other animals with testicular substance. But 

 these researches have not yet led to satisfactory and sufficiently 

 definite results. However, from the whole of the data collected 

 it may be affirmed with sufficient certainty that in normal and 

 sexually mature individuals the administration of testicular 

 tissue is generally without effect; but in those sexually im- 

 mature it accelerates the appearance of the secondary sexual 

 characteristics and arrests prematurely osseous development ; nor 

 is it without effect on castrated animals for example, young 



FIG. 42. Interstitial cells of testicle of man, with Reinke's crystals. 

 Magnified 300 diameters. (Prenant.) 



capons in which it serves to prevent and correct the consequences 

 of castration, so far as it has influence on the organism as a whole ; 

 in these cases it distinctly improves the development of the comb 

 and gills, and brings back the processes of ossification to their 

 normal course. 



But above all appear to us definite and important the results 

 obtained by Loewy in relation to the exchange of material, the 

 amount of which increases for six to seven days in succession. 

 While awaiting more precise knowledge as to the chemical nature 

 of the specific active substances which exist and accumulate in 

 the testicles, and are capable of producing the effects which we 

 have described, we may ask ourselves whether the presumed 

 internal secretion of these organs is produced by the same epi- 

 thelial elements as those which are responsible for the external 

 secretion, that is spermatogenesis, or by other specific secretory 

 elements contained in the substance of the testicles. It is known 



