166 MAN --AN ADAPTIVE MECHANISM 



determine whether or not the lesions in the brain, the 

 adrenals and the liver caused by exhaustion could be 

 repaired by rest without sleep, other animals were first 

 fatigued by physical exertion and then kept awake 



A. B. 



Section of normal cerebellum of Section of cerebellum of rabbit after 

 rabbit. insomnia 100 hours. 



FIG. 24. PHOTOMICROGRAPHS SHOWING THE EFFECT OF INSOMNIA 100 

 HOURS ON THE BRAIN-CELLS OF A RABBIT. 



Compare the well-stained clearly defined Purkinje cells along the margins 

 of section A with the faint traces of the Purkinje cells which are barely 

 visible along the margins of section B. 



(From photomicrographs, X 100.) 



for eight hours, their tissues being compared with those 

 of similarly fatigued animals which were allowed imme- 

 diate sleep. In every case we made histologic examina- 



