THE THYROID GLAND AND ITS DISEASES 241 



are not altered qualitatively, but their rate is increased when thyroid 

 derivatives are administered. 



The so-called antitoxic action of the thyroid is probably directly re- 

 lated to its metabolic function. The diminution of the alexins and opso- 

 nins (vide supra) in thyroidectomized animals may be a natural result 

 of retarded exchange of material in the tissues and will render the animals 

 more liable to infection. 



It would seem that iodin, in certain organic combinations, is valuable 

 as a catalytic agent in aiding or hastening the fundamental metabolic 

 activities of the body. The thyroid is an organ whose function is to utilize 

 this fact for the needs of the economy. 10 



"Kendall believes that the essential part of the active substance is the NH 2 COOH 

 group, and that the iodin modifies the action, but is not essential. But he has not yet 

 succeeded in preparing the active nucleus without iodin. "Thyroxin" has now, I 

 believe, been synthesized on a commercial scale. 



