iv THE GENEEATIVE SYSTEM OF THE MALE 153 



age become psycho-asthenic, melancholic, and paranoic. In these 

 effects of emasculation on the whole organism one has physiological 

 proof that the determinants of the secondary male characteristics 

 are not contained in the sexual organism arising from the germ, 

 but depend on the development of the testicles; for when these 

 are removed during childhood, those characteristics do not 

 develop. The testicles, therefore, exercise independently of their 

 sexual function, which during puberty is accompanied by con- 

 siderable somatic and psychic phenomena, a most important 

 trophic influence which extends to almost all the organs and 

 tissues of the economy. This correlation of the genital organs 

 with the nutrition and development of the other tissues of the 

 entire organism opens a large field of work to which, up to recent 

 times, physiological research had not been directed. 



To account for this correlation, the view which almost ex- 

 clusively prevailed in the past was that the testicles during the 

 whole time of their full functional activity exercised by means 

 of their centripetal nerves a continuous tonic action, which was 

 transmitted by the sympathetic through the sacral plexus to the 

 cerebro-spinal nervous system, and thus produced reflex trophic 

 effects more or less diffused over the whole organism. This 

 opinion was maintained by the most distinguished physiologists, 

 including Pfliiger, who were inclined to consider the nervous 

 system as the supreme centraliser, dominator, and regulator of 

 all the functions of the organism. 



There are not wanting data which may be adduced to support 

 this view. The multiform trophic effects which manifest them- 

 selves in consequence of castration, although diffuse, do not occur 

 equally in all the organs, or in all the tissues constituted alike ; for 

 instance, it hinders the development of the hairs of the beard, and 

 not those of the head ; it arrests the development of the laryngeal 

 cartilages, and not that of the other cartilages. If a stag be 

 castrated bilaterally after he has lost his old horns, he does not 

 develop new horns; if, on the other hand, he is castrated uni- 

 laterally, the horn renews itself only on the side not operated on. 

 The horns of the castrated bull become like those of cows ; 

 castration of the boar limits the development of the so-called 

 tusks; in the cock, the growth of the comb and spurs. These 

 localised trophic influences are very difficult to explain without 

 admitting a nervous influence which is transmitted from the 

 testicles especially to the affected tissues and organs (Samuel). 



Many other effects of castration, however, are explained more 

 simply by the theory that the testicles produce, in addition to 

 the external secretion destined for the most important function 

 of reproduction, a special internal secretion capable of influencing 

 chemically the other tissues. Let us review shortly the facts. 

 A first series of researches upon the presumed internal secretion 



