296 STUDIES IN ADVANCED PHYSIOLOGY. 



Function. The function of this gland has not been made 

 satisfactorily clear. When the gland is removed from the 

 body peculiar pathological symptoms result, associated with 

 mental disturbances which finally result in insanity and death. 

 It has therefore been supposed by some physiologists that 

 this gland normally removes from the body a kind of poison 

 which, when it accumulates, causes all these pathological 

 symptoms. Such physiologists would look upon the thyroid 

 body as an anti-toxine agent. In fact, certain observers 

 have tried to establish that in animals deprived of the thy- 

 roid body there was actually an accumulation of poisons in 

 the blood to such an extent that when this blood was in- 

 jected into other animals it poisoned them. The difficulty 

 of taking into consideration all possible errors in such an 

 experiment makes it impossible to rely with assurance up- 

 on its results, and more recently physiologists have gone to 

 the view that the thyroid glands do not remove a substance 

 from the body which is injurious, but produce a substance 

 for the body which is not only beneficial but indispensable. 

 Experiments have been made by injecting extracts of the 

 thyroid gland into animals, the result being a beneficial 

 quickening of the general body metabolism. Physiologists 

 holding this view would explain the pathological symptoms 

 which follow the loss of these glands, such as the diminu- 

 tion of muscular strength, failure of the mental powers, 

 swelling of the connective tissues, and excessive dry ness of 

 the skin, as a result of the absence of this necessary tonic 

 secreted in the thyroids, and it ought therefore to follow, if 

 this view is correct, that the administration of an extract of 

 the thyroid gland ought to" produce the normal condition. It 

 is a remarkable fact that in human beings suffering from 

 such symptoms as the result of the loss of the function of 

 the thyroid, injections of thyroid extract, or even feeding 

 them some fresh gland soon restores the individual to a 

 practically normal condition. 



It is unfortunate, from a physiological point of view, 

 that a gland which seems to play such an important role in 



