TRACT OF LISSAUER 123 



13. According to the observations of Rosenzweig and others, 

 the substantia gelatinosa contains many nerve cells, mostly of 

 small size, and a fine plexus of dendrites. 



14. The tract of Lissauer, the intermediate layer of vertical 

 fibers, and the substantia gelatinosa Rolandi are all intimately 

 related to each other, and, taken together, form a complex sys- 

 tem, the function of which is as yet unknown. Rosenzweig 

 thinks that the substantia gelatinosa has a sensory function. 

 Sano thinks that it may have an intimate relation to the sym- 

 pathetic system, exerting a vasomotor and pilomotor control. 

 He even suggests that it may be the locus of the cells of origin 

 of efferent fibers in the dorsal roots. In view of the non-medul- 

 lated character of most of the fibers belonging to this system, 

 Sano's theory is especially interesting. 



15. I believe we are justified in offering as a tentative inter- 

 pretation the suggestion that we are dealing here with the ap- 

 paratus for pain and temperature sensations. The non-medul- 

 lated fibers of the dorsal roots have been shown to arise from 

 the small cells of the spinal ganglion which are typical unipolar 

 cells with T-shaped processes (Ranson '12). That is to say, 

 from the location and form of the cells of origin of these fibers 

 one may safely assume that they are afferent in function. They 

 can have nothing to do with the afferent impulses which come 

 from the muscles and joints, since these sensations travel up- 

 ward in the fasciculus cuneatus and fasciculus gracilis, which 

 contain practically none of these fibers. On the other hand, 

 pain and temperature are known to pursue a different course in 

 the cord from that taken by the muscle sense, passing into the 

 gray matter near the level at which they enter the cord. This 

 would correspond to the course of the non-medullated fibers 

 since they are short and run in Lissauer's tract for only a short 

 distance before entering the substantia gelatinosa. It is in- 

 teresting to note that Ziehen has attributed to this part of the 

 cord the function of conducting pain and temperature sensations. 

 No data is at hand, however, as to how these sensations pass 

 from one side of the cord to the other, although there is an 

 abundance of fine commissural fibers to which this might pos- 



