( 39 ) 



brain-stem of the rat. In man we meet with about the same relative 

 position; in most other mammals the cells remain radior fronlallj 



Fig. 21. Makropus rebus lus. 



to the motor quintns-nuclens ; the nncl. infero-posterior (Cajal) lies 

 somewhat caiidally to the trochlear exit beside the 4*'' ventricle (cat, 

 horse). 



The position of the cells in the cross plane also exhibits but 

 gradual differences between each other. A real medio-dorsally situated 

 nucleus as in didelphia is nowhere to be found. Nevertheless in one 

 group of mammals [carnb'ora pinnipecUa) of which I examined 

 phoca viiuUna a tendency in this direction can be observed. The 

 general situation here is that the cells keep their dorsal position, 

 and in the region of the commissura posterior the position of a few, 

 well dev^eloped cells strongly recalls that of the medial nucleus 

 already discussed (fig. 23). The cat exhibits nothing of this, although 

 in general the cells lie rather more dorsally on the border of the 

 subst. grisea centralis than in the case of rodentia, insectivora and man. 



