THE COURSE WITHIN THE SPINAL CORD OF THE 



NON-MEDULLATED FIBERS OF THE DORSAL 



ROOTS: A STUDY OF LISSAUER'S TRACT 



IN THE CAT 



S. WALTER RANSON 



From the Anatomical Laboratory of the Northwestern University Medical School 



ELEVEN FIGURES 



It has been shown that the small nerve cells of the spinal gan- 

 glia give rise to non-medullated axons, each of which divides 

 dichotomously into a small non-medullated fiber running toward 

 the periphery and an even smaller one centrally directed in the 

 dorsal root. These non-medullated fibers can be followed for long 

 distanced in the nerve on the one hand, and through the dorsal 

 roots to the spinal cord on the other. Just as the small cells of 

 the ganglion far outnumber the large cells, so the non-medullated 

 fibers of the nerve and the dorsal root far outnumber those which 

 are medullated. Since these facts with the related literature ha\'e 

 recently been discussed in detail (Ranson '11, '12) it will be unnec- 

 essary to repeat them at length in this place. 



Partly with reference to this problem and partly with reference 

 to the variations in the pyramidal tracts, we have recently been 

 studying the spinal cord in a number of mammals. In looking 

 over the accumulated material it became evident that the sec- 

 tions of the spinal cord of the cat were especially suited for the 

 solution of the problem of the central course of the afferent spinal 

 non-medullated fibers. In fact, the course of these fibers stands 

 out with diagrammatic clearness in the pyridine-silver prepara- 

 tions of the spinal cord of the cat. 



259 



THE JOURNAL OP COMPARATIVE NEtlROLOGY, VOL. 23, XO. 4 

 AUGUST, 1913 



