CENTRAL NERVOUS SYSTEM. 



193 



Table showing the Decrease in the Volume of the Nucleus of Stimulated Spinal 

 Ganglion-cells of Cats. Stimulation for fifteen seconds alternating with 

 rest for forty -five seconds (Hodge). 



Stimulation continued for 

 1 hour. 

 2.5 hours. 

 5 

 10 



Shrinkage in the volume of the 

 nuclei of the stimulated cells. 



22 per cent. 



21 " 



24 " 



44 " 



This table further shows that the shrinkage is greater, the greater the 

 time during which the stimulus was applied. There is thus established not 

 only the fact of a change in the cell, but also a relation between the amount 

 of this change and the length of time during which the stimulus was allowed 

 to act. The results when expressed by a curve yield the following : 



Hours 1 2£ 



10 11' 



17 



23 



29 



Fig. 82 —The broken line indicates the volume of the nuclei of the spinal ganglion-cells of a cat 

 after stimulation for the times indicated. The solid line indicates the volume of the nuclei, first after 

 severe stimulation for five hours, and then in other cats, also stimulated for five hours, but subsequently 

 allowed to rest for different periods of time. The period of rest is found by subtracting five hours from 

 the time at which the record is made. After twenty-four hours of rest the nucleus is seen to have 

 regained its normal volume (Hodge). 



Whether these changes could be considered similar to the normal physio- 

 logical variations depended on whether it was possible to demonstrate recovery 

 from them. This was accomplished in the following manner : 



Under fixed conditions a cat was stimulated in the usual way and the 

 amount of shrinkage in the nuclei of the spinal ganglion-cells was determined. 

 This was found to be almost 50 per cent. Four other cats were similarly 

 treated and then allowed various periods (six and a half, twelve, seventeen, 

 and twenty-four hours) in which to recover. The results appear in Fig. 82. 



Having thus shown that the change was physiological in the sense thai it 

 was one from which the cells could recover, it remained to be shown that the 

 features of the change were discernible in the living cell, and were not caused 

 secondarily by the actions of the reagents employed in preparing the sections. 



For the study of' the living cell, frogs were chosen, and the cells of the 

 sympathetic ganglia examined. In these experiments, cells from different 

 frogs were prepared under two different microscopes and kept alive in the 

 Vol. II.— 13 



