961 



nated dorsal roots I have seen some non-inediiilated fibres, but 

 ihey have never occurred in my preparations in as great numbers 

 as R. seems to have seen them. A large number of these liner fibres 

 have, as one finds on closer investigation, a medullary sheath, 

 although rather a thin one. This fact has caused me to undertake 

 a closer and renewed examination of the question of the relation 

 between the total number of nerve fibres in the dorsal root and the 

 total number of ganglion cells in the spinal ganglion belonging 

 to this. 



From the right side of a 3,5 years' old dog the spinal g'anglia 

 with their dorsal roots from Th VI, L IV and L VII were taken. 

 After fixation and silver-impregnation (according to my modifications 

 of the B. -method) the spinal ganglia were put in unbroken series 

 of sections, lb [i thick, and the cross-sections at h and c fig. 1 were 

 made 10 n thick. 



The results obtained were as follows: 



Th. VI. Total number of ganglion-cells = 8422 



,, ,, ,, nerve-fibres at ^ = 6198 



,, ,, ,, ,, ,, c = o297 



L IV. Total number of ganglion cells =12181 



,, ,, ,, nerve-fibres at b = 9003 



,. ., ,, ,, ,, C := 9oll 



L VII. Total number of ganglion cells =29621 

 ,, ,, ,, nerve-fibres at ^ = 23627 



,, ,, ,, ,, ,, c =3 2o9o / 



These figures show that, although each nerve fibre in the dorsal 

 root is counted, one does not reach the total number of the spinal 

 ganglion cells. This is also the case if one counts the nerve fibres 

 situated immediately peripherally from the spinal ganglion. The 

 slightly larger values of the latter nerve fibres are all within the 

 limit error in calculation (± 2 per cent). Thus one cannot conclude 

 from these figures that the nerve fibres which issue out of the spinal 

 ganglion into the nerve are more numerous than those which form 

 the dorsal root. It was noticeable that the medullary sheaths were 

 more powerfully developed at c than at h fig. 1. On the strength 

 of the results of my own investigations I wish to state that Ranson 

 goes too far, and that the other writers who have worked with the 

 method of medullary sheaths do not go far enough in their con- 

 clusions with regard to the relation between the number of ganglion 

 cells and the number of nerve fibres in the dorsal root. Here, as 

 in so many other cases, the motto "in medio Veritas" applies. Thus, 

 in spite of Ranson, we must take into account the fact that the 



