lissauer's tract in the cat 273 



SUMMARY 



1. The small cells of the spinal ganglion give rise to non- 

 medullated fibers whose centrally directed branches form the non- 

 medullated fibers of the dorsal roots. 



2. The non-medullated fibers of the dorsal roots can be traced 

 with diagrammatic clearness into Lissauer's tract. 



3. The tract of Lissauer contains rather sparsely arranged fine 

 medullated fibers which are in part derived from the dorsal roots 

 but are in greater part of endogenous origin. 



4. The tract of Lissauer contains a very great number of fine 

 non-medullated axons, at least the great majority of which are 

 derived from the non-medullated fibers of the dorsal roots. 



5. It is probable that the substantia gelatinosa is the nucleus 

 of reception for the non-medullated fibers. 



6. It seems clear that the non-medullated fibers have little or 

 nothing to do with the transmission of the afferent impulses from 

 the muscles and joints, at least with such part of these impulses 

 as are transmitted upward in the posterior funiculi. 



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