SECRETION OF THE DUCTLESS GLANDS. 871 



or immature thyroid tissue. At the same time it is becoming 

 generally recognized that different as the functions of these two 

 tissues may be, they are in some way correlated, and that the 

 removal of one of them influences the activity of the other. 



The Function of the Thyroid. According to the opinion 

 of most writers on the subject, removal of the thyroid alone, 

 leaving, at least, the external parathyroids uninjured, is followed 

 by the development of a state of chronic malnutrition which 

 expresses itself finally in a condition of cachexia. Following a 

 terminology sometimes used in medical literature, this cachectic 

 condition may be designated as " cachexia thyreopriva," whereas 

 the convulsive condition or tetany, formerly also described as a 

 symptom of loss of the thyroid, is due rather to removal of the 

 parathyroid, and may be characterized as "tetania parathyreo- 

 priva." No adequate explanation has been furnished of the in- 

 fluence exercised by the thyroid on the nutrition of the body. It 

 is usually assumed that the thyroid cells form an internal secretion 

 containing a specific hormone which acts as a chemical stimulus to 

 other tissues, causing an augmentation of their metabolism. 

 Some justification for this view is found in the effect of feeding 

 thyroid tissue to normal individuals. The result in such cases is a 

 marked increase in the excretion of nitrogen and an augmentation 

 of the oxidations of the body, as shown by an increase in the output 

 of carbon dioxid. On this basis the tissue has been administered 

 for the purpose of reducing the body fat in cases of adiposity, but 

 the details of its influence on the metabolic processes are for the 

 most part unknown, and when used beyond certain limits it may 

 cause heart effects and other disturbances of a pathological nature. 

 In the condition known as exophthalmic goiter there is evidence 

 that the thyroids are hypertrophied, and some of the symptoms of 

 this disease are explicable as the results of an oversecretion of the 

 active hormone, that is to say, there is a condition of hyperthy- 

 roidism. As was stated above, Baumann isolated from the thyroid 

 a peculiar substance, iodothyrin, which is characterized chemically 

 by its large percentage of iodin, and physiologically by the fact 

 that when used upon patients suffering from a deficiency in func- 

 tional activity of the thyroid (myxedema, goiter) it gives beneficial 

 results. In the gland this iodothyrin is combined with protein to 

 form a thyreoglobulin or thyreoprotein. There has been much 

 discussion regarding the iodin constituent of the thyroid tissue. 

 Extensive observations have shown that in some entirely healthy 

 animals iodin is absent or is present only in traces, and in animals 

 in which it is present the amount may vary greatly with the char- 

 acter of the food. Hunt gives the following table: 



