804 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



As to the cause of the symptoms, many possibilities have to be considered, 

 in the first place, no direct relationship exists between the thyroid and 

 parathyroid in this connection. One cause might be the absence of 

 some substance which checks the activity of the nervous system, some 

 chalone in Schafer's sense. It was previously thought by W. G. Macal- 

 lum 46 that, since, nervous symptoms like those of tetany could be pro- 

 duced by deficiency of calcium in the body and the symptoms of parathy- 

 roidectomy were relieved by the administration of this cation, calcium 

 deficiency was the cause of the symptoms. The defective calcification of 

 the bones and teeth following parathyroid deprivation together with the 

 frequent association of rickets (a condition characterized by a modified 

 calcium metabolism) enhanced the plausibility of such an hypothesis. 

 On the other hand, that no view can be correct which takes as its basis 

 the absence or deficiency of some one or other substance which is sup- 

 posed, normally, to influence the activity of nervous tissues is indicated 

 by the fact that blood-letting or the transfusion of normal saline imme- 

 diately removes the symptoms, and keeps them in abeyance for some time. 

 Moreover, such a view does not adequately explain the metabolic dis- 

 turbances, which may continue when the nervous symptoms are slight as, 

 for example, after the administration of calcium. The most probable ex- 

 planation of the beneficial effect of calcium upon the nervous symptoms is 

 that it behaves merely as a sedative, reducing the excitability of the 

 nervous system, an action which it is known to possess. 



While not denying that calcium ions may have some minor relation- 

 ship to the symptoms, Noel Paton ascribes them chiefly to intoxication 

 by guanidine (page 640). The evidence is as follows: (1) Guanidine 

 or methyl guanidine administered to normal animals produces symp- 

 toms that are identical with those following parathyroidectomy. (2) 

 No drug, other than guanidine, which can effect a decided increase in 

 the excitability of the motor nerve endings to the constant current, has 

 been found. (3) There is a marked increase in the amount of these sub- 

 stances in the blood and urine of parathyroidectomized dogs, and in 

 the urine of children suffering from idiopathic tetany. It is also true 

 that while creatine (which contains the guanidine nucleus and is a prob- 

 able source of this substance) is absent from the urine of healthy adults, 

 it is normally present in the urines of children between the ages of 12 

 and 15 years, a period during which the incidence of tetany is most 

 frequent. Under 6 months creatinuria does not usually occur, tetany 

 also is extremely rare at this age. These facts taken in conjunction with 

 the other evidence, seem to have more than a coincidental bearing upon 

 the genesis of tetany. (4) In certain cases, the serum of parathyroidecto- 

 mized dogs acts upon the muscles of the frog similarly to weak solutions 

 of guanidine. (5) There is a striking similarity in the relative amounts 

 of the nitrogenous metabolites in the urine of parathyroidectomized dogs 



