INTERNAL SECRETIONS 357 



experiment of itself, however, does not preclude the possibility that the active 

 constituents of the extract are products of post-mortem changes and have 

 therefore no real significance normally. In order to establish the presence 

 of an internal secretion, one must demonstrate that the venous blood flowing 

 from the organ exercises a specific influence upon the bodily functions, also 

 that the extirpation of the organ produces disturbances which are not due 

 to accidental lesions, and which eventually disappear on transplantation of 

 the organ or upon administration of its extract. 



B. THE TESTES 



It has long been known that castration produces a series of profound 

 changes in both men and animals. A steer which has been castrated loses 

 the vehement strength of the bull and becomes a relatively tractable and 

 quiet animal. If a boy be castrated, his voice does not change as it otherwise 

 would at puberty, but retains more of the high register of the childish voice. 

 The power and endurance of the eunuch's muscles are not those of a fully 

 grown man, but are as a rule soft and flabby. His body frequently has a 

 bloated appearance and becomes very corpulent. The amount of oxygen ab- 

 sorbed also declines after castration. Aside from their sexual functions, which 

 call forth profound physical and psychical phenomena at the time of sexual 

 heat, the testes, therefore, exercise a very marked influence over the entire 

 body. 



It might be supposed that this influence is mediated in some way by the 

 afferent nerves of the testes. But even if this were true and we do not know 

 that it is still other circumstances would have to be considered. If both testes 

 be removed from a very young cock, and pieces of them be grafted into the 

 abdominal cavity, the secondary sexual characters which are otherwise wanting 

 after castration make their appearance much as usual. Since the testes were 

 in this case entirely separated from their nervous connections, their influence 

 can only be explained from the viewpoint of an internal secretion (Foges). 



The compounds given off to the body are probably the same as the active 

 constituents of a glycerin extract of the testis, the subcutaneous injection of 

 which, according to Brown-Sequard, raises the tonus and power of the neuro- 

 muscular mechanisms and acts favorably upon the bodily conditions in general. 



On the basis of Brown-Sequard's recommendation, testicular extract has 

 found a very extensive use in the treatment of various forms of weakness. It 

 was often assumed that the unquestionably favorable effects were psychical, for 

 it is well known that very often a medicine, of itself absolutely without effect, 

 produces a very marked improvement or even cures all sorts of nervous dis- 

 orders if only the patient is convinced beforehand that he will be cured. It has 

 been shown, however, by means of experiments, which appear to be entirely 

 trustworthy, that the extract really favors the action of muscular exercise either 

 by raising the power of the neuromuscular apparatus, by diminishing its exhaus- 

 tibility or by improving its ability to recover. This effect lasts for a long time 

 after the conclusion of exercise and after the injections have ceased, and dis- 

 appears very gradually (Pregl and Zoth). Even on the isolated heart perfused 

 with blood testicular extract exerts a distinct and powerful effect (Hedbom). 



The active substance of the extract has not yet been isolated and is known 

 only in solution. The seat of ijs action in favoring muscular exercise is not 

 definitely known, but is probably central. 



