THE THYROID APPARATUS 



neutralizing activity of the thyroid gland. He thinks that these 

 results are sufficiently explained by the changes in metabolism 

 produced by the thyroid substances. And, certainly, the evidence 

 in favour of a neutralizing activity on the part of the thyroid 

 gland cannot yet be regarded as sufficient, seeing that such 

 activity is manifested only in regard to acetonitril, and only in 

 mice. Moreover, the resistance of animals, including mice, to 

 other toxins, as, for instance, morphine, is not only not increased, 

 but is appreciably lowered by thyroid extract. It is interesting 

 to note in this connection that the blood of persons with Graves's 

 disease produces the same increased resistance to acetonitril in 

 mice as thyroid extract. This may be regarded as evidence in 

 favour of a hyperthyrosis in Graves's disease. 



It is evident, then, that direct proofs of the neutralizing 

 function of the thyroid gland are not forthcoming, and that the 

 indirect proofs advanced by Reid Hunt are capable of another 

 interpretation. Such being the case, the hypothesis of an anti- 

 toxic thyroid function must be allowed to remain sub judice. 

 At the time when the symptoms of thyroid suppression were re- 

 garded as manifestations of an acute auto-intoxication, this 

 hypothesis was obvious and perhaps even necessary. To-day, it 

 not only appears unproven, but, in the light of our present know- 

 ledge of the function of the thyroid gland, it is in reality 

 superfluous. 



All the known phenomena, both physiological and patho- 

 logical, associated w r ith the activity of the thyroid gland, are 

 sufficiently accounted for by the following interpretation of the 

 thyroid function. 



The thyroid gland is a secretory organ, the end-product of 

 the secretory activity of \vhich is supplied to the blood in the 

 form of an iodized albuminoid. Inasmuch as it modifies the 

 activity of distant organs, this substance behaves as a hormone. 

 As far as we know at present the thyroid secretion, by promoting 

 katabolism and increasing normal function, plays the part of 

 disassimilatory hormone to a large number of tissues and pro- 

 cesses. This disassimilatory activity principally affects the 

 metabolic processes, the cardiac activity, some portions of the 

 sympathetic system, and certain of the internal secretory organs 

 (hypophysis, suprarenals). Certain phenomena in other parts of 

 the body suggest, however, that the thyroid secretion also 

 possesses an inhibitory function and contains, therefore, an 

 assimilatory hormone. The promotion of skeletal growth, the 

 development of the sexual glands, and the limitation of the internal 

 secretory function of the pancreas, are instances of such assimila- 

 tory activity. 



The question arises as to whether this two-fold and 

 antagonistic activity on the part of the thyroid secretion is due 

 to the action of two different hormones ; or whether the results 



