138 HODGE. [Vol. VII. 



its own by the tribute rendered to it even by muscle, I had 

 expected to find the power to recover much more energetic in 

 the nerve cell than in gland cells, the process of recovery in 

 which has received some attention (on this point see 39, p. 587). 

 No attempt to draw any exact time parallel between the action 

 of the gastric cells of a frog and the spinal ganglion cells of a 

 kitten is to be understood from the present reference. It is, 

 however, of interest to note in this connection that Langley and 

 Sewall found that, upon feeding a frog, the granules commenced 

 to pass out of the cells of the stomach, and continued to do so 

 for about six hours, when they began to fill up the cells again, 

 and recovery was not complete until twenty-four hours had 

 elapsed (34, p. ^'J^i). That is, to recover from six hours' secre- 

 tion required twenty-four hours' rest.^ 



VI. Curve of Nerve Cell Fatigue and Recovery. 



In the foregoing, data are present from which to construct a 

 curve that may provisionally, at least, be taken to represent the 

 process of fatigue and recovery in the cells of the spinal gan- 

 glia. Whether these results are applicable to the action of 

 other kinds of nerve cells, it is impossible to say with certainty. 

 And whether the action of the nucleus may be fairly considered 

 an index of the whole process is open to question. But we 

 have shown that this shrinkage of the nucleus is directly pro- 

 portional to the duration and also to the intensity of stimula- 

 tion, and, in general, inversely proportional to the length of 

 the period of rest. At any rate, it is the only index we have at 

 present, and we may be permitted to use it with the understand- 

 ing that the curve obtained is entirely provisional. 



The curve of fatigue for a muscle is generally described as a 

 straight line which falls more or less abruptly according to its 

 load, and the strength and frequency of stimuli applied to it. 

 The fatigue of a muscle in situ is, moreover, an exceedingly 

 slow process {39, p. 547), if a physiological process at all. Roth 

 stimulated muscles continuously for as long as twenty days 



1 It will be remembered that, if a frog is fed a piece of sponge instead of a worm, 

 recovery may be greatly slowed. In another series of experiments I shall attempt 

 feeding regularly. However, Langley's experiments and my own in this respect are 

 clearly not comparable, since sponge acted to produce a much longer stimulation 

 than food. 



