Hardestv, spinal Ganglion Cells. 5 i 



ber of cells per fiber in the dorsal root is greater than in the older 

 specimens, but the difference is not so great as one would be 

 led to expect nor do the ratios of the individual sums show a 

 variation decreasing with the increase in weight. Rather, the 

 relations between the number of cells and the number of dor- 

 sal root fibers seem to be maintained approximately constant in 

 the nerves here employed. All this can hardly be due to chance 

 variations in the fixed number of cells in the individual ganglia 

 of the different frogs. 



With Hatai's enumerations for a mammal, the results are 

 different. Using a similar tabulation of his numbers for the 

 three nerves of the rat (Table V) it appears that, with the in- 

 crease from the average weight of 17.4 grams to that of 118 

 grams, the ganglion cells undergo an increase of only \2% 

 while the dorsal root fibers increase 80% and the ratio between 

 the two is considerably higher in the younger than in the adult. 

 Hatai ('02) notes that in some of the nerves of the rat of 10.3 

 grams, the ratio of fibers to cells is as much as 1:1 1, while in the 

 older it may be as low as 1:3. Based on this great decrease of 

 the ratio with the progress of growth and the relatively small 

 actual increase in the cells of the individual nerves of the different 

 specimens, he concludes that the number of ganglion cells in the 

 white rat remains approximately constant between the weight 

 of 10.3 grams and the adult. He interprets the differences as 

 probabl)- due to individual variations in the ganglia of the dif- 

 ferent specimens employed and cites the fact that the 24. 5 gram 

 rat gives a sum of cells in the three nerves chosen which is less 

 than that of the rat of 10.3 grams. Donaldson ('02) supports 

 the views of Hatai and in discussing the investigation, lends 

 observations which strengthen it. 



Hatai states that the only argument in favor of an increase 

 in the number of cells with age is the fact that of the four speci- 

 mens employed the two older gave combined a greater number 

 of cells than the two younger. Table V here given groups the 

 older against the younger in order to compare the results with 

 those from the frog in Table IV. The difference between the 

 averages of the two groups of rats amounts to about 3200 cells. 



