50 



BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



showing that the demands of waking life had resulted in par- 

 tial exhaustion of their stock of force-producing materials. 



Fig. 3. 



Fig. 4. 



Fig. 3. — Two sections, A and B. from the first thoracic spinal ganglion of a cat. 

 B is from the ganglion which had been electrically stimulated through Ita 

 nerve for five hours, A from the corresponding resting ganglion. The 

 shrinkage of the structures connected with the stimulated cells is the most 

 marked general change. N, nucleus ; N. S., nucleus of the capsule ; V., va- 

 cuole x 500 diameters. (Hodge.) 



y IG . 4. — Showing the change observed in the nucleus of the living sympathetic 

 nerve cell of the frog, as the result of electrical stimulation. At the beginning 

 of the experiment the nucleus is seen to be replete with what we may call 

 potential nerve energy : but after thirty minutes of stimulation it appears 

 somewhat shrunken, and the shrinking increases as the experiment proceeds. 

 At the end of six hours and forty-nine minutes the shrinking of the nucleus 

 Is very marked. (Donaldson, 1 after Hodge.) 



§3. Neural Fatigue: Its Nature and Motor Effects. — Mod- 

 ern science then conceives of the brain as a generator and reser- 

 voir, so to speak, of energy which is essential to the activity 

 of body or mind. A proposition growing out of this is self- 

 evident, — that when one's resources are expended in one direc- 



1 Growth of the Brain, p. 320. 



