The Lower Portion of the HunKin Brain-Stem. 49 



aspect of the nuclei fasciculorum gracilis et cuneati. In the upper two- 

 fifths of the nucleus the cell-column becomes flattened, so that the long axis 

 lies in the dorso-ventral i)lane. Al)out the middle of the nucleus there 

 occurs a well-marked, narrow, ventral spur; just cephalic to this are two 

 smaller and less well-marked dorso-mesial spurs. At the level of the more 

 cephalic of these spurs a marked dorsal concavity occurs on the ventral 

 border, compensated b}^ a corresponding dorsal convexity. Cephalic to 

 the curving resulting from that concavity and convexity, the nucleus resumes 

 its straight course. From mesial view the cei)halic half of the nucleus 

 appears much larger than the caudal portion. This appearance is due only 

 in part to the flattening above recorded, but there is an actual increase in 

 the cross-section of the nuclear material. The mesial surface of this cephalic 

 half of the nucleus is rendered irregular and rough by slight depressions 

 and ridges. Just before its cephalic termination, at a point where the nucleus 

 vestibularis medialis and the substantia gelatinosa come into contact, the 

 nucleus of the tractus solitarius exhibits an abrupt dorsal shoulder which 

 rounds out into the cephalic pole. This dorsal beak-like projection lies just 

 lateral and cephalic to a ventral projection from the nucleus ahe cinerete. The 

 lateral surface of the ujjper two-fifths of the nucleus conforms to the curve 

 of the mesial surface of the nucleus of the fasciculus cuneatus. 



NUCLEUS OF ROLLER. 



The nucleus, described by Roller (1881) as a "small-cell hypoglossal 

 nucleus," has been modeled in this reconstruction. It lies in the superior 

 dorsal depression on the ventral surface of the nucleus nervi h^vpoglossi 

 (figure 4). In its long cephalo-caudal diameter it measures 3.3 millimeters 

 and has an average transverse diameter of 0.8 millimeter. 



Roller described the nucleus as lying about in the middle extent of the 

 hypoglossal nucleus. As seen from mesial view (figure 4), the nucleus lies 

 ventral to the cephalic one-third of this nucleus of the twelfth nerve instead 

 of in its middle region. It does lie, however, in the middle of the complex 

 of nuclei nervi hypoglossi et intercalatus. The nucleus is composed of much 

 smaller nerve-cells than those found in the hypoglossal and is separated from 

 the nucleus by transversely coursing fibers (figure 11). 



The nucleus may be described as a round column of cells presenting 

 some slight surface irregularities. Its dorsal surface is cur\ed to conform 

 with the ventral surface of the hypoglossal nucleus, but on mesial view the 

 ventral border shows an independent form (figure 4). Beginning caudally 

 in the very sharp pole, the ventral border runs directly cei)halad for a short 

 distance and then turns in a sharp bend into a straight border running 

 cephalad and dorsally to the upi^er pole, which is tapering and sharp. The 

 nuclear mass widens and broadens quickly from its sharp caudal pole and 

 continues as a rounded column for two-thirds of its length. Cephalic to 

 this it tapers into its superior pole. The dorso-ventral and transverse 



