30 A Reconstruction of the Nuclear Masses in 



The dorsal border at its caudal extremity is continued at almost a right 

 angle in the short, straight caudal border which extends in a ventral and 

 lateral direction. This is rather abruptly rounded into the ventral border, 

 which runs cephalad, with dorsal and lateral deviations. The ventral border 

 is by no means straight. For a short distance after its caudal inception, it 

 parallels the dorsal border, then loses most of the dorsal deflection as the 

 nucleus widens. This change of direction results in a marked dorsal notch. 

 Superior to this, the ventral border continues in a slightly irregular line to a 

 ]:)oint just above the level of the dorsal angle of the nucleus, where it shows a 

 ventral bulging and thickening, due to the dorsal convexity of its border 

 cephalic to this. This dorsal convexity of the ventral border, more marked 

 at its ends than in its middle, is continued into a ventral projection of the 

 nucleus just below the cephalic termination of the nucleus tractus solitarii. 

 Above this ventral beak-like projection the ventral border curves abruptly 

 dorsally into the superior pole of the nucleus. Just cephalic to the ventral 

 bulging of the nucleus about its middle portion, the ventral border splits 

 into a second line, which runs cephalad in a slight, dorsally convex margin. 

 Between this margin and the real ventral border occurs a triangularly 

 shaped ventral surface. The apex of this triangle lies in the ventral projec- 

 tion in the cephalic portion of the nucleus; the base is formed by the 

 border between the mesial and ventral surfaces. This line of junction 

 between these two surfaces continues upward, to end in a small ventral spur 

 which lies mesial to and projects somewhat ventrally to the ventral cephalic 

 border. This ventral surface shows a fairly smooth curving face, the con- 

 vexity being dorsal and lateral. 



The dorso-lateral surface of the nucleus ala; cinerese is found only in 

 the cephalic one-third of the nuclear mass (figure 3). It is a small irregular 

 surface, just ventral to the dorsal border, narrower above than below, and 

 jjossessing an irregular anterior border. This margin is composed of the 

 ventral-lateral projections of the nucleus around the tractus solitarius, which 

 is almost inclosed by two horns of this nucleus. This margin is irregular, 

 but maintains a direct cephalo-caudal direction. Below, at the j miction of 

 the cephalic one-third and the caudal two-thirds of the nucleus, is a deep 

 sulcus which separates it from the mesial surface. In the upper portion the 

 dorso-lateral surface looks dorsally and somewhat laterally, but by a gradual 

 rotation the surface in its caudal portion looks laterally and only somewhat 

 dorsally. 



The lateral surface of the nucleus is a very irregular but, in general, 

 smooth area which is embraced between the ventral border, the lower two- 

 thirds of the dorsal border, and the ventral margin of the dorso-lateral 

 surface. Cephalad, it is a concave depression which surrounds the dorso- 

 mcsial aspect of the tractus solitarius. The horns of this embracing surface 

 arc the ventral margin of the dorso-lateral surface and the ventral border 

 of the nucleus. The surface begins mcsially and cephalad on the lateral 



