114 S. WALTER RANSON 



merous fibers are seen passing back and forth at all angles. The 

 two structures are, in fact, most intimately associated and there 

 is no sharp line of separation between them. 



LISSAUER'S TRACT IN THE CAT 



The tract of Lissauer in the cat has been described in detail in 

 another paper. In shape and position it is very similar to the 

 dorsal part of the tract in the monkey. It presents the same 

 differences in shape and position in the three principal regions of 

 the cord. In the cat it shows a tendency to spread out ventro- 

 laterally, since the ventral part of the tract fades off gradually 

 into the lateral funiculus. The chief difference in the two ani- 

 mals is, then, the great development of the lateral part of the 

 tract in the monkey, of which there is only a suggestion in the 

 cat. 



The tract has the same structure as in the monkey. It is 

 possible to follow a few medullated and a large number of non- 

 medullated fibers into it from the dorsal roots. No oblique 

 fibers either medullated or non-medullated could be followed 

 into the tract from the ground bundle of the lateral funiculus. 

 The substantia gelatinosa and the tract of Lissauer show the 

 same interchange of fibers in the cat as in the monkey. 



LISSAUER'S TRACT IN THE RABBIT 



In the rodents the substantia gelatinosa Rolandi is highly de- 

 veloped, in some much more so than in others. Associated with 

 the large and varying size of the substantia gelatinosa there are 

 corresponding changes in the tract of Lissauer. There are more 

 differences, so far as this tract is concerned, between the rabbit 

 and the white rat than between the rabbit and man; and the 

 study of the tract in the rodents is therefore of special interest. 



Because of the similarity of the tract of Lissauer in the rabbit 

 to that in higher mammals only a brief account need be given. 

 In the seventh cervical segment the substantia gelatinosa is 

 somewhat nearer the surface than in the same part of the mon- 

 key cord. The tract is about as long (antero-posteriorly) as 



