556 A MANUAL OF PHYSIOLOGY 



frogs, and it is doubtful whether they can be extended to mammals. 

 But if these nerves end in the pancreas, and do not simply run 

 through it, say, to the liver, it is possible that they act on the sugar 

 metabolism by regulating the internal secretion of the pancreas. 



Sexual Organs. The influence of castration in preventing 

 the physical and psychical changes that normally occur at 

 puberty is no doubt also, in part at least, due to the loss of the 

 internal secretion of the testes. In partially castrated cocks 

 it was seen that so long as a portion of one testicle remained, the 

 male characters were preserved, but after removal of this 

 residue the comb and wattles withered in a few weeks (Hanau) . 

 At the breeding-time the muscles of the forearm of the brown 

 land frog (Rana fusca) become hypertrophied in the male, so 

 that it can more tightly hold the female. At the same time the 

 balls of the toes increase in size, and become covered with a 

 peculiar black growth. After the breeding season these secondary 

 sexual characters disappear. If the male frog is castrated, the 

 periodical return of these phenomena does not occur, but the 

 presence of one testicle suffices for their development on both 

 sides. When pieces of testicle from normal frogs are introduced 

 under the skin of the castrated frogs, the phenomena occur just 

 as if the animals had not been castrated (M. Nussbaum). The 

 exact experiments of Loewy and Richter on the metabolism 

 of bitches before and after castration throw light upon the 

 changes which follow that operation, and afford decisive proof 

 that they are connected with the absence of substances specific 

 to the ovary. They conclude that in the castrated animal the 

 oxidative energy of the cells is lessened. The oxygen consump- 

 tion sinks, even although protein is laid on and the total amount 

 of active tissue thus increased. Under certain circumstances 

 this specific diminution of metabolism may be balanced by 

 conditions which cause an increase in the metabolism. The 

 lessening of the oxidative power is due to the loss of ovarian 

 substance, for the administration of an extract of the ovary 

 (oophorin) not only neutralizes it, but actually causes an increase 

 in the gaseous metabolism to far above the original amount, 

 while it has no effect on the metabolism of the uncastrated 

 animal. It is not the decomposition of proteins, but of non- 

 nitrogenous substances, which is accelerated. Oophorin also 

 brings about a notable increase in metabolism in the castrated 

 male dog, while, curiously enough, extract of testicle causes 

 only a small increase, due to a basic substance, spermin (C 5 N 2 H 14 ), 

 which can be isolated from the testicle. But the orchitic 

 extract is not without influence in other ways. It certainly 

 increases the capacity for muscular work, as tested by the 

 ergograph (p. 650), and this distinct physiological action is 



