74 S. WALTER RANSON 



AN INTERPRETATION OF SOME OF THE LITERATURE ON THE 

 SPINAJ^ GANCiLION IN THE LIGHT OF THESE OBSERVATIONS 

 WITH REMARKS ON THE SOURCE OF THE NON-MEDULATED 

 FIBERS. 



In order to show how the presence of these non-niediillated 

 fibers clears up many obscure questions m previous histological, 

 numerical, and experimental observations on the primary sen- 

 sory spinal neurones it will be desirable to present a summary of 

 some of the known facts concerning the spinal ga'nglion cells and 

 their processes. At the same time evidence will be presented to 

 show that the non-medullated fibers are the axons of the small 

 cells of the spinal ganglia. The accurate data, relating to the 

 numerical relations in the spinal nerves, which have been accumu- 

 lated under the direction of Dr. Donaldson, formed the starting 

 point for this investigation ; as they now form one of the chief argu- 

 ments in favor of the correctness of the observations herein 

 recorded. 



1. Axons of the spinal ganglion cells 



The vast majority of the cells of the dorsal root ganglia are 

 associated with axons which branch dichotomously into central 

 fibers, which run in the dorsal root, and peripheral fibers, which 

 run in the nerve. A careful reading of Dogiel's book ''Der Bau 

 der Spinalganglien " ('08) will show that our views concerning 

 this fundamental point, while obscured bj^ an astonishing wealth 

 of detail, have not been materially altered. In six (i, ii, v, vi, vii, 

 x) of his eleven types this branching occurred. In type ix the 

 cells were bipolar with centrally and peripherally directed fibers. 

 In types iii, iv and xi he was unable to determine the destination 

 of the axon, but in only one type (type viii) did he find the dis- 

 tribution of the axon different from that which has been commonly 

 accepted. 



Nissl's ('03) idea that the dorsal root fibers are independent of 

 the spinal ganglion cells, merely passing through the ganglion, 

 has received no support and has already been sufficiently dis- 

 cussed in a previous paper ('08). We will be not far from right 



