24 PHYSIOLOGY CHAP. 



thyroid arteries, by reducing the quantity of blood that flows to 

 the brain. 



The fallacy of Cyon's theory becomes obvious when we 

 remember, on the one hand, that the effects of thyroidectomy are 

 totally avoided in dogs by preserving the two upper halves of the 

 two thyroid lobes (Sanquirico and Canalis), or even one upper half 

 of one lobe (Colzi) ; on the other, the double clinical syndrome of 

 cachexia and tetany exhibited in man after extirpation of the 

 thyroid, with the various associations and successions of the two 

 categories of phenomena consequent on thyroidectomy in dogs. 

 The most direct and convincing refutation of Cyon's hypothesis, 

 however, lies in other important experimental facts which must 

 now be examined. 



VIII. We have seen that the first generic proof of the theory 

 which regards the sequelae of thyroidectomy as phenomena of 

 auto-intoxication from accumulation in the blood of the katabolic 

 products of the various tissues, resulted from the direct reciprocal 

 transfusion between two dogs, one dethyroidised and the other 

 normal, as performed under our directions by Colzi in our 

 laboratory. The conclusion we arrived at of the protective 

 antitoxic function of the thyroid gland, was too important for the 

 work not to be taken up and repeated by many investigators and 

 with various methods. 



Eogowitsch (1886-88) was the first to verify these results. 

 Next in order, with more variation in detail, came the experiments 

 of Fano and Zander (1889), and of Lusena (1889). 



Starting from these fundamental notions, Gley (1895) con- 

 ceived the happy idea of comparing the degree of toxicity of blood 

 serum from a healthy dog with that of a dog suffering from tetany 

 and cachexia thyreopriva, by injecting these sera into frogs, 

 guinea-pigs, and rabbits. He came to the conclusion that the 

 toxicity of the serum of dethyroidised dogs, as compared with that 

 of the normal dog, is exhibited in these animals by different and 

 more acute symptoms, i.e., by severe convulsions. 



The toxicity of the urine in dethyroidised animals also increases 

 relatively to that of the urine of healthy animals. This fact, 

 which was at first denied by Alonzo (1890), was clearly established 

 by Gley (1894), and was subsequently confirmed by Laulanie and 

 by Maison (1894). 



Eeasoning from this fact, which shows that the toxic substances 

 that accumulate in the blood after thyroidectomy are eliminated 

 by the organism through the renal excretory system, Dutto and 

 Lo Monaco (1895) were led to suspect that the intoxication 

 consequent on thyroidectomy occurred by a process analogous to 

 that which produces uraemia, more particularly as the symptom- 

 atology of the latter is no less varied, and presents not a few points 

 of resemblance with cachexia thyreopriva. This suggestion was 



