104 



furrow beti«33n the miibPiin anJ the cer.3b3llntn. hohon evident- 

 ly sought for the nucleus of the nerv^e near its superficial 

 origin, for he identified as such a group of cells on the bor- 

 der of the cerebellum. 



The group of neurones constituting the nucleus of the IV 

 nerve lies posterior and slightly ventral to the nucleus of 

 the Til nerve (?ig.53,n.IV) . The anterior end of the trochlear 

 nucleus overlaps the posterior end of the oculonotor nucleus 

 for a short distance. 



The cells of this collection are, as compared v»ith the 

 cells of the oculomotor nucleus, decidedly smaller in size, 

 and the general outline is more nearly triangular. Tne nucle- 

 us of the cell is relatively larger in proportion to the amount 

 of cytoplasm. The chromatic network is so delicate as to be 

 but faintly visible even under high magnification. 



The masses of tigroid substance are few in number, rel- 

 atively large in size, and wholly irregular as to form. There 

 is a perinuclear zone of cytoplasm entirely free from tigroids. 

 it often appears as though many of tne tigroid masses are act- 

 ually clinging to the limiting pellicula of the cell. Pig.'^O 

 exhibits a condition typical for the cells of this group. 



I really am unable to offer any explanation concerning 

 the marked differences to be observed between the tigroid- 

 bodies of the trochlear and the oculomotor neurones, respect- 

 ively. The contrast in both the form anJ the arrangement of 

 the tigroids is quite evident. The distinction is a real one. 



