604 LECTURE XXVI. 



what they were, and the attempts to isolate the active principle contained 

 in the organ were fruitless. Here again we have observations from the 

 fields of physiology and of pathology at our disposal. We shall begin 

 with the latter. The thyroid gland frequently shows signs of degenera- 

 tion, and this apparently takes place in a definite manner, and is most 

 common in definite localities. These are the so-called goitre regions; i.e., 

 regions in which there is frequently a cystic deformity producing an 

 enlargement of the thyroid. The nature of the soil, and especially of 

 the drinking-water, has been assumed to be the cause of the disease, with- 

 out any one being able to show this conclusively. Frequently other 

 severe derangements accompany the deformity of the gland. The mental 

 development of those afflicted with the disease is slight. Such individuals 

 are known as cretins. There is a derangement of their entire metabolism. 

 Scholz 1 in particular, who studied a case very carefully, showed this to be 

 true of the metabolism of albumin and salts. We are justified in assum- 

 ing, as we shall soon see, that the thyroid gland has not ceased entirely 

 to exercise its function. It seems highly probable that we shall realize 

 more closely the part taken by the thyroid gland in metabolism, if we 

 assume that it has different functions. We can well imagine that in 

 cretinism it is possible for the thyroid to retain certain of its functions 

 while others are missing. 



An idea as to the complete function of the thyroid gland is probably to 

 be obtained best by studying an organism after the complete ablation of 

 the organ. The operation has been performed upon man as well as upon 

 animals; in the first case, however, only at a time when we were not yet 

 ready to study the whole consequence of the interference. To-day it is 

 well recognized that the organ is quite essential, so that care is taken not 

 to remove it completely. We may say, in this connection, that a small 

 portion of the gland left in the body is usually sufficient for the retaining 

 of all the functions of the organ. This fact should be well borne in mind, 

 for it gives us the key to the cause of many contradictions which are to be 

 found in the literature. The thyroid gland itself is an unpaired organ. 

 Anatomically it is usually homogeneous. Embryologically it arises from 

 clefts or bronchial arches at the lower part of the epithelium of the 

 pharynx. Often, however, we find near the main gland isolated fragments 

 of similar material in the surrounding tissue, and frequently these are 

 quite far from the main gland. In the ablation of the latter, they may 

 assume its functions, so that the typical results of the operation are not 

 felt. Entirely distinct from the thyroid gland are the parathyroid glands. 

 They are paired, and originate from the last pair of clefts of the pharyn- 

 geal epithelium. We shall find, later on, that their position relatively to 



1 Z. exper. Path. u. Therap. 2, 271 (1905). 



