236 SWALE VINCENT 



at any ra^e when large doses are given. The symptoms observed were 

 loss of body weight, gastro-enteritis, and diarrhea. Thyroid feeding does 

 not produce tachycardia, nervousness or exophthalmos. Although the, 

 symptoms in experimental animals may be those of "hyperthroidism" 

 they are not those of exophthalmic goiter. According to Carlson and 

 his co-workers, man is very susceptible to 1 thyroid feeding and the 

 expression of hyperthyroidism in the human subject may differ from 

 that in the lower animals. 



Thyroid substance is toxic, while substance prepared from brain, 

 liver, spleen, kidney, and skeletal muscle is not toxic. The toxic substance 

 is not due to autolysis or decomposition, and is not simply an excess of 

 protein in the food. (French.) 



In the case of animals very susceptible to thyroid feeding, dogs' 

 normal thyroids are more toxic than the hypertrophied thyroids. As the 

 latter contain less iodin, the toxicity of the dog's thyroid is directly 

 proportional to its iodin content, (Stoland.) 



Dogs, cats and rabbits show the same relative resistance to thyroid 

 pressure liquid introduced intravenously and to thyroid given by the 

 mouth. (Caldwell.) 



According to Kendall (d) (1917) thyroid and adrenal cortex must act 

 together in order to produce "hyperthyroidism." 



How far the toxic effects referred to above are due to iodin qua iodin 

 has not yet been fully investigated, but Swingle (a) (&) has pointed out 

 that since all the symptoms of "hyperthyroidism" can be produced in thy- 

 roidless frog larvae by overfeeding with iodin, it is logical to suppose that 

 the symptoms of hyperthyroidism in man are due to the same cause. 9 The 

 whole difficulty at the present time lies in the fact that the symptoms of 

 thyroid feeding in animals do not appear to be those of "hyperthyroidism" 

 in man. 



The Influence of the Thyroid upon Metabolism 



In 1893 it was noticed that when patients suffering from myxedema 

 were fed with thyroid gland substance there was a rapid loss in body 

 weight, due to diminution of subcutaneous fat and water. From that 

 time up to the present thyroid preparations have been used with good 

 results to reduce obesity. 



The study of this effect led to a series of experiments on the influence 

 of the administration of thyroid glands upon metabolism. The majority 

 of observers recorded a distinct increase of nitrogen in the urine, with a 

 concomitant decrease in weight, indicating an increased protein metab- 

 olism. 



8 The symptoms of "iodism" in man are not, however, those of hyperthyroidism. 



