i8o Journal of Comparative Neurology, 



lions, which are fused with those of the vagus. Near the 

 brain, however, it turns cephalad, and soon divides into two 

 bundles, IX^+^ and IX^+^ The first is the 1st Vago-glossopha- 

 ryngeal root of Strong, (IX^ of Osborn), and the representa- 

 tive of the lateral line nerve of fishes (Strong) ; IX^+* is IX^+^ 

 of Osborn, 2nd root of Strong. 



IX^+^ is the more caudal and is formed of two roots. The 

 fasciculus communis gives off a large contingent to form IX^; it 

 passes dorsad to the ascending fibers of the eighth. IX^ springs 

 from the motor cells in the floor of the oblongata and passes 

 ventrad of the ascending fibers of the auditory, to its exit, join- 

 ing IX^ immediately. There is an exact agreement in the above 

 with the results of Osborn and Strong. 



The other division is composed of fibers of a very charac- 

 teristic and constant appearance. They are large, with very 

 dense myelinic sheaths, and are of the same appearance in all 

 the forms studied. This bundle proceeds cephalad a short dis- 

 tance and enters the dorsal region between the tracts here called 

 a and b, by two roots, one more dorsal and slightly cephalad of 

 the other, and separated from it by a small fasciculus of longi- 

 tudinal fibers. Some of the fibers of each root lose their 

 myelin almost immediately on entering the brain and disappear; 

 others may be traced cephalad for a few sections, but are lost 

 within a quarter of a millimeter from the point of entrance. 

 None of the fibers were observed to turn caudad within the 

 brain. 



The region into which these roots enter contains but small 

 scattered bundles of myelinic fibers, of which the largest, on the 

 ectal surface of the brain, separates the two roots. An inter- 

 change of fibers occurs immediately cephalad of the roots. 

 Many arcuate fibers go to the dorsal tracts at this level. The 

 cinerea that adjoins the dorsal tracts at and cephalad of the en- 

 trance of this nerve is composed of small cells and must be re- 

 garded as the terminal nidus. 



An extensive comparative discussion of this nerve is given 

 by Strong ('95). The lateral branch of the vagus, or more cor- 

 rectly perhaps the lateral nerve, has been likewise found to arise 



