490 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



the fibres become lost at the lower extremity of the medulla 

 oblongata, and around which at the same point the lateral and 

 the posterior columns of the spinal cord coalesce. It is conse- 

 quently recognizable as the gelatinous substance or caput 

 cornu. The quantity of this gelatinous substance appears to 

 have undergone extraordinary increase in the lower half of the 

 medulla oblongata, being accumulated to form the grey tu- 

 bercle of Rolando, because at these levels the chief portion of 

 the ascending root of the fifth is developed from it as a centre 

 (figs. 261, 262, (7). Nerve corpuscles of larger calibre, foreign to 

 the gelatinous formation, but which are included in it at various 

 heights of the pons and medulla oblongata, I am of opinion, 

 may be regarded as introduced by traversing masses of the 

 fibrae arcuatse, and in part by traversing nerve roots. 



4. Cerebellar roots of the fifth. These fasciculi, that in all 

 probability enter the fifth pair of nerves, traverse and embrace 

 the superior peduncle of the cerebellum, and Stilling has al- 

 ready ascribed a similar course to them (figs. 252, 253, 5 d). 



It is certainly satisfactory to find that in the mode of ori- 

 gin of a pair of nerves connected with so many and various 

 peripheral regions a corresponding multiplicity of anatomical 

 relations can be established. On the other hand, however, 

 while giving the objective enumeration of these origins, such 

 considerations must be neglected, because for the present we 

 possess no sufficient grounds for a systematic theory furnishing 

 a key to their comprehension. 



Below the origin of the fifth, the grey floor of the fourth ven- 

 tricle is divided by symmetrical lateral grooves into the median 

 territory of origin of the sixth and seventh cerebral nerves, and 

 into the lateral origin of the auditory nerve (fig. 254, G and 8). 



The nervus abducens (fig. 254, 6) springs from Stilling's 

 abducens-facialis nucleus, a cluster of slender multicaudate 

 nerve corpuscles (fig. 254, on the left side, in front of 6r) two 

 millimeters broad and T6 millimeters thick in section, the cells 

 of which have for the most part a length of 45 p, and a 

 breadth of 15 //. 



This nucleus, according to Stilling and Schroder v. d. Kolk, 

 is connected with the raphe by means of the most posterior 

 fibrse arcuatse. By following up the fasciculi I have satisfied 



