878 PHYSIOLOGY OF DIGESTION AND SECRETION. 



cysts containing colloidal material. Most observers, however, 

 take the view outlined above, that the parathyroids have a func- 

 tional significance essentially different from that of the thyroids, 

 and that the parathyroids as they exist in the body are not simply 

 undeveloped or immature thyroid tissue. 



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 maybe 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. 

 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. More 

 striking results have been obtained from calorimetric observations 

 upon cases of exophthalmic goiter and cretinism. In the former 

 condition it is supposed that there is a hypersecretion of the thyroid 

 bodies, and Du Bois* reports that in such cases the basal metab- 

 olism is greatly augmented, the increase amounting to 75 per cent, 

 or more when reckoned on the basis of calories of heat produced per 

 square meter of skin area. Expressed in this unit the metabolism 

 of a normal person is 39.7 calories per square meter; that of a case 

 of exophthalmic goiter as much as 75 calories. On the other hand, 

 in cretinism and in myxedema, in which there is a reduced activity 

 of the thyroid body, the basal metabolism is reduced below normal. 

 It would seem to follow from these facts that the internal secretion 

 of this gland must have a profound and probably variable influence 

 on metabolism. The way in which this influence is exerted and 



* Du Bois, "Archives of Internal Medicine, 17, 915, 1916. 



