THE PAKATHYBOID GLANDS 551 



Experimental Physiology, 1917, to which the reader is referred for de- 

 tails. As stated briefly by Paton, "the parathyroids control the metabolism 

 of guanidin in the body by preventing its development in undue amounts." 

 The cause of parathyroid tetany is guanidin intoxication acting on the 

 central nervous system and peripherally on the myoneural junctions. 

 According to Koch, "a mother substance from which guanidin may be 

 formed is cyanamid, a body which may be recovered in methylated form 

 from the urine of parathyroidectomized dogs. The cyanamid can readily 

 take up ammonia to form guanidin. If not so converted to guanidiri, it is 

 readily hydrated into urea." 



The main facts in favor of the guanidin intoxication theory are, first, 

 that symptoms identical with those of parathyroidectomy may be pro- 

 duced' in animals by the injection of soluble salts of guanidin; that guan- 

 idin is^ greatly increased in the blood and urine of animals suffering from 

 parathyroid tetany; that nerve muscle preparations are affected alike by 

 solutions of guanidin and by the serum of animals in parathyroid tetany ; 

 and that articles of diet rich in creatin, such as meat, greatly aggravate 

 the symptoms. 



One of the circumstances most difficult to explain in* experimental para- 

 thyroidectomy has been the divergent results obtained by competent oper- 

 ators, using different species of animals. The predecessors of Gley ex- 

 plained this on dietetic grounds, and future investigation may show that 

 the results depend more largely on metabolic changes than the theory of 

 the indispensability of the parathyroids will allow. 



Paton also believes that tetania parathyreopriva and idiopathic tetany 

 are due to the same cause, viz., diminution or suppression of parathyroid 

 function. Histological evidence on this point has, however, so far, not been 

 conclusive. 



Chemistry of the Parathyroid Glands 



Our knowledge of the chemistry of the parathyroids is, as yet, very 

 imperfect. In 1897 Gley (c) reported the presence of iodin in these glands 

 in the rabbit and dog in comparatively large quantities. He used the 

 method of Baumann, somewhat modified, and attempted to estimate quan- 

 titatively the iodin in the thyroid and parathyroids of each animal sepa- 

 rately. He presents his results in tabular form in six rabbits and five 

 dogs, and his conclusion is that in the rabbit the amount of iodin found 

 in the parathyroids is actually greater (about 2.35 times) than that in 

 the thyroid, while relatively it is much greater (about 37 times). In the 

 dog, while the absolute amount found in the parathyroids was less than 

 in the thyroid, relatively it was much higher. 



From the fact that, according to his findings, Gley believed that both 



