TRACT OF LISSAUER 99 



ill i)art correct and that the medullated fibers in this tract are 

 in jiai't endogenous and in part exogenous. It is probable that 

 the endogenous hbers predominate. 



In fact, the most recent work on this subject tends further to 

 discredit the observations of Lissauer. Leszlenyi ('12) made a 

 comparative study of the tract of Lissauer and states that, while 

 in man and many animals horizontal medullated fibers cross the 

 tract to enter the substantia gelatinosa, the dorsal roots con- 

 tribute practically nothing to the vertical fibers of the tract. 



And, as we shall see, the observations of Kolliker and others 

 on Golgi preparations are to be explained on another basis than 

 that furnished by Lissauer's observations. In the cat it has 

 been shown (Ranson '13) that the non-medullated fibers of the 

 dorsal roots separate out from among the medullated fiber just 

 before the rootlet enters the cord, and turning laterally they 

 enter the tract of Lissauer. Alost of the fibers of the lateral 

 bundle of the dorsal root seen in Golgi preparations of the cord 

 of newborn animals are fibers which never acquire a myelin 

 sheath. The picture of an entering rootlet which is given by a 

 pyridine-silver preparation of the spinal cord of an adult cat is 

 very similar to that given by the CJolgi method in the newborn 

 animal, and very different from that seen in Pal-Weigert prep- 

 arations of the adult cord. 



We wish in this paper to present a study of the entering root- 

 lets and tract of Lissauer in man, the rhesus monkey, the cat, 

 rabbit, sc^uirrel, guinea-pig, and albino rat, and to present at 

 the same time some notes on the character of a closely associated 

 structure — the substantia gelatinosa Rolandi. 



TECHNIQUE 



For the demonstration of the myelin sheaths sections were 

 stained by the Pal-Weigert method. In differentiating these 

 some sections were not fully decolorized in order to make sure 

 that no fine medullated fibers were lost. The axons were stained 

 by the pyridine-silver technique, the details of which were given 

 in a previous paper (Ranson '11). In some cords, namely, those 



