170 MAN --AN ADAPTIVE MECHANISM 



Another group of animals, kept awake for from 90 

 to 112 hours, instead of being allowed to sleep naturally, 

 were placed for eight hours under nitrous oxid anesthe- 



A. B. 



Section of normal adrenal of cat. Section of adrenal of cat showing 



effect of extreme physical exertion. 



FIG. 28. PHOTOMICROGRAPHS SHOWING THE EFFECT OF EXERTION ON 

 THE ADRENALS OF A CAT. 



In B, note the general loss of cytoplasm and the disappearance of many 

 nuclei. 



(From photomicrographs, X 1640.) 



sia. Of the brain cells of these animals ninety per cent 

 were found to be hyperchromatic, resembling closely 

 the abnormally large percentage of hyperchromatic 



