The Motor Ganglion Cells of the Frorfs Spinal Cord. 77 



The great difference between the fibres and cells of frog 

 49, was a surprise to me. It is, however, easily explained. 

 As already said, the nervous elements in a small frog are 

 smaller than in the larger ones. There are thus a larger 

 number proportionately of small (jells and fibers. But 

 while osmic acid discriminates easily from the smallest 

 fibres, the corresponding cells are hardly distinguishable 

 from the large embryonic cells found in great numbers in 

 the cord of developing frogs, like the one in question. I 

 therefore suppose that the number given for the fibres is 

 probably the true number for the cells. 



I append a figure in which the weight of the frog serves as 

 the axis of abscissas, and the number of ganglion cells and 

 nerve fibres as that of ordinates. It will be seen that there 

 is quite a close correspondence between the lines of cells and 

 and fibres, but that the former shows a too cupid decline in 

 the region of the smaller frogs. The lines should probably 

 run parallel and would do so were the methods for discrim- 

 inating cells as good as those for fibres. 



In Fig. 1 the figures on the lower side of the cut represent the weight of 

 the frogs in gramnaes; those on the right of the cut, tlie number of cells 

 or fibres. The broken line represents the curve of the ganglion cells. The 

 upper line shows the nerve fibres, and the lower line the large ganglion 

 cells in those frogs where only those cells were counted. The numbers in, 

 the cut refer to those of the frogs examined. 



