THE THYROID AND PARATHYROID GLANDS 805 



and normal animals injected with guanidine, in either instance the total 

 nitrogen is increased and the proportion of urea diminished. 



It is concluded that the parathyroids control the metabolism of guani- 

 dine "by preventing its development in undue amounts. In this way 

 they probably exercise a regulative action upon the tone of the skeletal 

 muscles." 



Though the evidence of these observers is most formidable, it seems 

 that the question has not yet reached finality, for Howland and Mar- 

 riott 47 still insist that a lowered calcium content of the blood is responsi- 

 ble for idiopathic tetany. This contention is supported by a mass of 

 analytical data from which the fact is brought out that the blood of chil- 

 dren suffering from tetany shows a reduction of calcium, to the extent 

 of 40 per cent in many instances. The question whether this deficiency 

 is merely an accompaniment of the condition or the causative factor 

 does not appear to have been fully investigated. It is possible that neither 

 of these factors guanidine formation or calcium deficiency is the pri- 

 mary cause of tetany, but that one or perhaps both may be secondary to 

 some condition as yet unrevealed. 



