THE THYROID AND PARATHYROIDS 319 



principle or principles is probably under the control of the 

 sympathetic. Whether the influence of the active material 

 is direct on the tissues themselves, or indirect through the 

 nervous system, is still doubtful. The thyroid is not equally 

 important in all groups of animals. Adult herbivora can live 

 in good health without a thyroid while the carnivora under 

 such conditions will frequently suffer severely and die. 



Kendall regards the action of the thyroid substance as 

 that of a catalytic agent. The substance does not alter the 

 character of the fundamental reactions but increases their rate. 



The antitoxic action of the thyroid gland depends in all 

 probability on its metabolic function. The slowed changes 

 of material in the body after removal of the thyroid will 

 diminish the amount of alexins and opsonins and so render 

 the animals more liable to infection. Regarding the perplexing 

 problem of the iodine, it seems wise to assume provisionally 

 that this element, in certain organic combinations, is of service 

 as a catalytic agent in aiding or accelerating the fundamental 

 metabolic processes of the body. We may also assume that 

 the thyroid has for its function the utilization of the iodine in 

 the diet to build up the particular compound or compounds 

 which are necessary. Kendall believes that the essential 

 part of the active substance is the NH 2 COOH group, and that 

 the iodine modifies the action, but is not essential. But he 

 has riot yet succeeded in preparing the active nucleus without 

 iodine. 



S. Extirpation Experiments upon the Parathyroid 

 Glandules 



The external parathyroids were discovered by Sandstrom in 

 1880. But it was not until their rediscovery by Gley in 1891, 

 and the description of the internal parathyroids by Kohn in 

 1895, that extirpation experiments could be carried out with 

 due regard to anatomical considerations. 



Vassale and Generali removed all four parathyroids from 

 nineteen animals ten cats and nine dogs leaving the thyroids 

 intact. Of the ten cats, nine succumbed within ten days, 

 most of them at about the fifth day after the operation, after 

 presenting a typical train of symptoms. There were fibrillary 

 twitchings, muscular spasms, psychical depression, stiff and 



