Io6 'Journal of Comparative Neurology and Psychology. 



small cells in the spinal ganglia of the VI C, IV T., and II L. 

 nerves of four white rats, ranging in weight from ten to one hun- 

 dred sixty-seven grams, and found that, while the total number of 

 cells in each ganglion remained approximately constant, there 

 was a constant increase in the number of large cells and a corre- 

 sponding decrease in the number of the small cells. This can only 

 mean that the small cells are developing into large ones, and that 

 therefore a considerable number of the former retain their capacity 

 for development at least during the growing period. 



It is of interest to note in this connection the observations made 

 by Hodge ('89) that after electrical stimulation of nerves it is 

 chiefly the large cells in the associated spinal ganglia that show the 

 effect of fatigue. Considering all the cells large which have 

 one diameter 50/« or over and those small which have not, a count 

 gives the following results: 



TABLE I. 



E^ect of Stimulating Ganglion Cells (Hodge). 

 In 100 Large Cells, Nuclei In ioo Small Cells, Nuclei 



Hodge did not attempt an explanation of these interesting 

 results; but in the light of the preceding discussion there seems to 

 be little room for doubt that these small unworked elements are 

 the immature cells of Hatai. 



In summing up this discussion concerning the functional sig- 

 nificance of the small cells of the spinal ganglion, it may be said 

 that the absence of mitosis in the spinal ganglia during extra- 

 uterine life excludes the possibility of their being young cells in 

 the sense of Rawitz. No more acceptable is the view of v. Len- 

 HOSSEK that they are elements, the development of which has been 

 permanently arrested; we must rather agree with Hatai that they 

 retain for a long time their capacity for development, that, in fact, 

 some of them are always in the process of transformation through- 

 out the growing period of the animal. During the time that they 

 are still undeveloped they do not show fatigue when the nerve is 

 stimulated electrically. It is not yet satisfactorily determined 

 whether they may serve as reserve cells capable of replacing the 

 mature neurones destroyed by trauma or disease. 



