INTKODUCTION 15 



resulting from suprarenal insufficiency. The experiments, however, did 

 not exclude the possibility that in the condition mentioned a slow acting 

 toxin might conceivably accumulate and thus cause the symptoms of 

 suprarenal deficiency. The possibility remains open, not only as regards 

 the suprarenals, but also as regards various other organs that their 

 extirpation may lead to a gradual intoxication which might materially 

 influence growth and the various functional processes. Likewise, a gland 

 of the "endocrin" congeries might remove from the blood stream certain 

 substances which normally hold in check a tendency to overgrowth of some 

 of the tissues. The increased size of castrated cockerels, that is capons, 

 might well be due to such a cause. 



Other possibilities -present themselves. The endocrin glands may 

 contribute to the blood stream bodies in the nature of amboceptors whereby 

 the tissue cells are enabled to assimilate different substances necessary for 

 their normal metabolism. Such a conception fits in fairly well with what 

 is known regarding the endocrin function of the pancreas. The internal 

 secretions may in some cases serve as catalyzers to facilitate the specific 

 chemical processes in the various body cells. Such an assumption has 

 been made by Plummer, and with much plausibility, in the case of the 

 thyroid secretion. Allen has gone so far as to suggest that certain of the 

 endocrin activities may even be dependent upon the manifestation of some 

 sort of energy of a nature as yet entirely unsuspected, as was the action 

 of radium a generation ago. 



In some instances the effects of administering endocrin gland sub- 

 stances by grafting or otherwise seem to be due, in part at least, to the 

 stimulation of latent cells of the corresponding organs. For example, a 

 case has been described by Morris (1916) in which a testicular graft was 

 implanted to compensate for atrophy of the gonads. The procedure 

 resulted in a marked development of the atrophic testes which had been 

 left in situ. Similarly, the use of thyroid material is said to stimulate 

 the thyroid glands. This assumption is sometimes referred to as "H'al- 

 lion's law." Indeed, some authors have even gone so far as to maintain 

 that the only way an endocrin product can produce significant therapeutic 

 effects in the body is by stimulating tissues similar to those from which 

 the product is derived. The "law," however, has not generally been ad- 

 mitted as valid. 



The major problem as regards the mediation of hormone influences is, 

 whether the body cells are affected directly or through the nervous system, 

 or in both ways simultaneously. In case of epinephrin there is abundant 

 evidence that the striking pharmacodynamic effects following its injection 

 are due to selective stimulation of the sympathetic nervous system. The 

 stimulation 'affects largely the neural terminals or, more specifically, the 

 neurocellular junctional material, the "receptive substance" of Langley. 

 Thus in organs supplied with stimulating sympathetic fibers epinephrin 



