MEDULLA OBLONGATA OF THE RAliliJT. 



9 



ward, or, more accurately, forward, and meet in the middle 

 line. The result of this is, that the tractus solitarius be- 

 comes buried by their growth, and their meeting in the middle 

 line forms the so-called raphe of the medulla. (Fig. G.) 



In the adult medulla the division line l)etween the 

 dorsal and ventral zones is indicated by the superior and 

 inferior fovea, but in the regions where they are deficient, 

 it can always be approximately determined by the position 

 of the tractus solitarius, which, it must be remembered, lies 

 within the dorsal zone, close to the boundary of the ventral. 



Fig. 6. 



(Minot, o81,) Section tliroiigli the meiluUa oblongata of Ilis's emln-yo CR. 



Ts^ tractus solitarius. X, vagus nerve. Rsch^ Randschleier. X//, liypoglossal 

 nerve. R, raphe. After W. His. 



These are, for our purposes, the salient points in His's 

 description of the development of the human medulla. 



I find that the development of the medulla of the 

 rabbit differs from this description in three particulars : 



1st. The tractus solitarius is formed from the V {\\\ 

 and VIII), IX, and X nerves. 



2d. The oval bundle and tractus solitarius are prob- 

 ably not completely homologous. 



3d. A total absence of the rhomboidal lijj. 



