192 MAN --AN ADAPTIVE MECHANISM 



ment with the experimental findings that anesthetics, 

 curare or any break in the muscle-brain connection 

 causes diminished muscular action and heat production. 







X 







** 



2awSc>*:. 



A. 



Section of normal cere- 

 bellum of dog. 



B. 



C. 



Section of cerebellum Section of cerebellum 

 of dog after thyroidec- of dog after continued 

 feeding with thyroid ex- 

 tract. 



tomy. 



FIG. 42. COMPARATIVE EFFECTS OF EXCISION OF THE THYROID AND OF 

 EXCESSIVE FEEDING WITH THYROID EXTRACT ON THE BRAIN-CELLS 

 OF DOGS. 



The harmful effect of withdrawing thyroid secretion from the organism 

 is shown in B in the high percentage of degenerated cells, the loss of chro- 

 matic material and complete disintegration of many cells. The effect of a 

 continuous activation of the system by excessive feeding with thyroid secre- 

 tion is evidenced in C by the presence of hyperchromatic cells, together with 

 some exhausted, degenerated cells. The cells in both B and C present a 

 marked contrast to the uniform stainability and clearly defined outlines of 

 the normal cells in A. 



(From photomicrographs, X 310.) 



Thyroid: In myxcedema thyroid deficiency one 

 of the cardinal symptoms is a persistent subnormal tem- 

 perature. Subjects of myxcedema, although prone to 

 infection, show but slight febrile response and succumb 



