957 



As this attempt to explain the increase actiiallj existing in the 

 number of nerve fibres in the dorsal and ventral roots of the spinal 

 nerves as a result of a division of the axons was unsuccessful, I 

 had to proceed to investigate other possibilities. The following possi- 

 bility' has now to be closely considered. 



Js it possible that a nerve-ceM may send off more ilian one axon in 

 the same direction? 



In order to be able to answer this question, I have carried out 

 investigations in two directions. 1 first investigated carefully the 

 preparations left over from the preceding series in which, of course, 

 whole spinal ganglia and parts of the ventral horn were set up in 

 unbroken series, and secondly I counted all the cells in a ventral 

 horn of a 10 days' old and of a 360 days' old N^ls musculus var. albus 

 — between the exits for two spinal nerves from corresponding 

 segments — and also all the cells in a spinal ganglion similarly 

 situated in the two animals. The values obtained for the numbei'S 

 of cells have been compared with the number of axons in the 

 corresponding ventral and dorsal roots. One cannot, of course, expect 

 to obtain in these two ways an answer to the aforesaid question 

 that would be a priori absolutely certain, but it seems to me that 

 they take us as far as we can generally go with morphological 

 methods of investigation. A careful investigation (of the above-men- 

 tioned unbroken series) of the nerve-cells in the ventral horns and 

 in the spinal ganglion did not produce a single figure to support 

 the supposition of more than one axon being sent off in the same 

 direction from the nerve-cell. It is certainly true that in the spinal 

 ganglion there were nerve-cells which have processes beside the 

 axon, but in no single case could these be followed up to a 7'-division. 

 Spinal ganglion-cells of this sort are described by Ransom ^) and 

 others. I am of the opinion that this part of the investigation produced 

 a negative result. 



With regard to the calculations as to the number of cells, they 

 showed that the number in the older specimen was certainly greater 

 than in the youuger one, but the difference is not so large compared 

 with the difference in the number of axons in the same specimens. 

 The number of axons seems thus to increase in a relatively higher 

 degree than the number of ganglion-cells during the post-embryonal 

 period. This fact seems, of course, to allow the |»ossibility that the 

 same nerve-cell might send more than one axon into, for instance, 

 the dorsal and ventral roots. There is, however, another and more 



1) L. c. 



62 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



