104 S. WALTER RANSON 



ullated fibers from the radicles into the tract tlian it is in either 

 the cervical or lumbar regions. In serial sections of the third 

 lumbar segment one can trace these fibers with ease. There is 

 a tendency for these fibers to group themselves near the surface 

 of the fila, they do not, however, form a compact layer on the 

 surface of the fila, as in the cat. In other words, the non-med- 

 ullated fibers are not entirely separated from among the medul- 

 lated fibers of the rootlet until after the entrance of the rootlet 

 into the cord. From the accumulation of non-medullated fibers 

 near the surface of the entering radicle bundles of non-medullated 

 fibers can be traced into the tract of Lissauer. The arrange- 

 ment, while in all essentials the same, is by no means so clear and 

 diagrammatic as in the cat. 



LISSAUER'S TRACT IX THE MONKEY: MACACUS RHESUS 



The spinal cord of the monkey is very favorable material for 

 the pyridine-silver techniciue. The preparations are quite as 

 good as those obtained from the cat, and considerably better 

 than those which I have been able to secure of the human cord, 

 or of that of the dog, pig, rabbit, squirrel, guinea-pig or rat. 

 All of these cords give uniformly much poorer pictures than those 

 of the monkey and cat. 



In the cervical cord (fig. 4, seg. C. 7) the gray substance includ- 

 ing the substantia gelatinosa occupies about four-fifths of the 

 total length of the columna posterior, the apex with the included 

 Lissauer's tract, one-fifth. The tract fills the apex and reaches 

 from the substantia gelatinosa to the surface of the cord. An 

 accumulation of subpial neuroglia is seen at its dorsal extremity 

 (in the drawing the subpial neuroglia and the pia are together 

 represented as a white band). The subpial layer of neuroglia, 

 as well as the accumulation at the apex of the columna posterior 

 and the septa which project into the substance of the cord, is 

 granular not fibrous in appearance. This shows that neuroglia 

 fibers are not differentiated and that there is no danger of con- 

 fusing neuroglia fibers with fine axons. The limit of the tract 

 is not sharp on the side toward the cuneate fasciculus; and there 



