i INTERNAL PROTECTIVE SECRETIONS 31 



they have a decided tendency to retain such halogens in the 

 body. When the organic supply of halogen comes to an end, as 

 may occur after months or even years, the characteristic symptoms 

 of thyro-parathyroid deficiency reappear. 



Bunge (1898), on the simple ground of analogy, propounded 

 the hypothesis that the protective antitoxic substance secreted 

 by the thyroid consists in an unstable protein compound, belonging 

 to the enzyme group, with the property of producing large effects 

 by infinitesimal doses. When poured into the blood along with 

 the colloidal substances, this enzyme would influence the metabo- 

 lism of the body and accelerate the elimination by the renal outlets 

 of the katabolic products as fast as these are formed. But as 

 yet no experiments are to hand in direct evidence of this 

 hypothesis. 



X. In order to explain the fact that some animals (rabbits 

 constantly, and dogs in certain rare cases) can bear the complete 

 ablation of the thyroid without injury, Schiff (supra) proposed 

 the hypothesis that the body contains another organ capable of 

 supplementing the functions of the thyroid. This hypothesis led 

 to a number of ineffective researches, with the object of determining 

 which this vicarious organ could be. 



Fano (1893) showed that the removal of one suprarenal 

 capsule, of the salivary glands, the ovaries, and a large portion of 

 the pancreas, produced no modification in the sequelae of subsequent 

 total thyroidectomy. 



That no functional relation exists between the thyroid and 

 the spleen was plainly shown by the experiments of Tizzoni and 

 Fileti (1883-84), of Sanquirico and Canalis (1884), of Ughetti and 

 Mattei (1885), and others. In 1893 Zanda revived the subject, 

 and stated that thyroidectomy was not fatal in dogs, if performed 

 about a month after splenectomy. Had these results been con- 

 firmed, they would have been of great importance, justifying the 

 hypothesis put forward by Zanda, that the spleen pours toxic 

 products into the blood, which the thyroid renders innocuous. 

 Unfortunately, the later experiments of Fano, Vassale, and Di 

 Brazza proved that dogs and cats, deprived of their spleen, were 

 liable more than a month afterwards to the effects of thyroid- 

 ectomy, like normal animals. 



The principal argument against the existence of any functional 

 relation between spleen and thyroid rests on the recent histological 

 work of Massenti and Coronedi on the first of these organs in the 

 dethyroidised dog. The spleen undergoes a process of sclerosis 

 and atrophy, which is the more advanced in proportion as the 

 survival power of the animal to thyro-parathyroidectomy is 

 greater. 



Nor was the work of Marie and Mobius, of Cadeac and Guinard 

 (1894), who sought to establish a functional relation between the 



