No. 2.] CHANGES IN NERVE CELLS. 159 



glion cells of frog, cat, dog, under electrical stimulation ; for spinal 

 glanglion and brain cells of English sparrow, pigeon, swallow, 

 and for brain cells of honey-bee, under normal fatigue : — 



A. For nucleus: i. Marked decrease in size. 2. Change 

 from smooth and rounded to a jagged, irregular outline. 3. Loss 

 of open reticulate appearance with darker stain. 



B. For cell-protoplasm : i . Slight shrinkage in size, with 

 vacuolation for spinal ganglia ; considerable shrinkage, with 

 enlargement of pericellular lymph space for cells of cerebrum and 

 cerebellum. 2. Lessened power to stain or to reduce osmic acid. 



C. For cell capsule, when present : Decrease in size of nuclei. 



D. Individual nerve cells, after electrical stimulation, recover, 

 if allowed to rest for a sufficient time. The process of recovery 

 is slow, from five hours' stimulation, being scarcely complete 

 after twenty-four hours' rest. 



E. Provisional curves have been constructed from direct 

 observations of the nerve cell to represent the processes of 

 fatigue and recovery. These curves indicate that the nerve cell 

 tires or rests rapidly at first, then slowly, then more rapidly 

 again. That is, the curve of nerve-cell rest or fatigue is not a 

 straight line. 



I part with this manuscript with the feeling that I have not 

 done justice either to my material or to the subject. Interrup- 

 tion has been unavoidable, and stress of other work great. It 

 is, at best, but a small beginning in a field the bounds of which 

 have opened out much faster than I have been able to advance. 

 With greater opportunity and facilities for work which Clark 

 University will afford, it is to be hoped that something may 

 be accomplished during the coming year. 



In order to properly define results already obtained, it will 

 be necessary to know two things. First, exactly what changes 

 take place in nerve cells under variations of food and water 

 supply. Second, what changes, if any, take place in nerve 

 cells from birth to death from old age, from "rejuvenation" to 

 "senescence." ^ 



University of Wisconsin, Madison, Wis. 

 Aug. 27, 1892. 



1 An abstract of the above paper with demonstration of specimens was given 

 before the American Physiological Society at the Congress of American Physicians 

 and Surgeons, Washington, D.C, September 22, 1891. 



