ARTICLES 249 



such, is not the true criterion of activity. The active com- 

 bination (Thyroxin, or CnHioOsNIa) has recently been isolated 

 by Kendall (191 8), who states that it has all the physiological 

 properties of thyroid itself. 



The Parathyroids. — It has already been noted that the 

 earliest thyroidectomies invariably included the parathyroids, 

 and hence the results were always accompanied by nervous 

 manifestations (tetany). Further, these cases were rapidly 

 fatal, but, as with the thyroid, exceptions occurred. There has 

 been much speculation as to the function of these small glan- 

 dules, some holding that the thyroid and parathyroids are 

 mutually antagonistic (Rudinger), others that they are mutually 

 dependent (Vincent). Macallum and Voegtlin (1909) believe 

 that the latter regulates calcium metabolism, for the adminis- 

 tration of calcium salts relieves tetany. There seems little 

 doubt, however, that the parathyroid secretion controls the 

 detoxication of guanidine, which is normally produced by the 

 muscles of the body. In parathyroidectomised animals, there 

 is an increase of guanidine in the blood, and after injection of 

 guanidine into a normal animal, the symptom complex of tetany 

 is produced [Noel Paton (19 16)]. An increase of guanidine 

 is also found in the blood of children suffering from tetany 

 and rickets. 



Conclusions. — ^The function of the th5rroid varies according 

 to age. In the young it hastens development, in the adult it 

 maintains the working of the body processes at a normal rate, 

 and in the aged it probably ceases to function. The active 

 principle of the thyroid is an organic compound of iodine whose 

 constitution may perhaps be represented by the formula 

 CuHioOsNI,. 



