IO4 INTERNAL SECRETION 



severe symptoms of reduced function, is illustrated by endemic 

 goitre and endemic cretinism, the etiological relationship between 

 which is well known. 



THEORY OF THE THYROID FUNCTION. 



We now proceed to utilize the foregoing descriptions of the 

 results of hypo- and athyrosis, of the activity of thyroid extract, 

 and of the appearances which accompany hyperthyrosis in man 

 and animals, as material for a more detailed account of the 

 functional activity of the thyroid gland. 



The thyroid gland was the first organ to be credited with an 

 internal secretory function, and it was in connection with the 

 thyroid that the two-fold aspect of this function was first sug- 

 gested. On the one hand, we have to do with a positive pro- 

 ductive activity on the part of the gland ; and, on the other, with 

 its neutralizing activity, or negative secretory function. Thus 

 two theories regarding the function of the internal secretory 

 organs arose, the one advocating a positive and metabolic activity, 

 the other what may be called a negative or antitoxic activity. 

 Both theories derived a measure of support from the neutralizing 

 function of the thyroid gland. And, to-day, it is very generally 

 believed that the secretion elaborated by the thyroid gland serves 

 to neutralize the toxic products which are formed in the course 

 of normal metabolism, or which are believed to be formed 

 abnormally, either qualitatively or quantitatively, upon sup- 

 pression of the function of the organ. The two theories are 

 opposed only in regard to the actual place where the process of 

 neutralization occurs. The secretion theory assumes that this 

 process takes place in the blood-stream, while the antitoxin theory 

 places the seat of operation within the thyroid gland itself. 



With an improved knowledge of the results which follow sup- 

 pression of the thyroid function and, more particularly, of the 

 acute nervous symptoms induced by thyroidectomy, it was very 

 natural that the idea of an auto-intoxication should present itself. 

 It was not until the discovery of the presence in the thyroid 

 gland of a body containing iodine, that its secretory activity 

 assumed a physiological significance. The results of a sub- 

 stitution therapy were, however, invariably regarded as due 

 to a neutralizing and antitoxic action on the part of the thyroid 

 extract. This view is still so widely accepted that it is expedient 

 to enter into a more detailed consideration of it. 



The antitoxic theory was first propounded by Notkin, and 

 was afterwards developed by F. Blum. It can have but few 

 supporters at this date among scientists whose views are based 

 upon their own clinical or experimental experiences. It is as well, 

 however, that the theory should be reviewed, because it was ad- 

 vanced by Blum in opposition to the views which he formerly 



