Notes upon the Brain of the Alligator. 153 



and cephalad to the eminentia acustica, and may be called emi- 

 nentia motoria trigeminalis. The cells are of large size and of the 

 strict pyramidal form, affording a typical illustration of a motor 

 cell. An apical process from each cell, directed obliquely periph- 

 erad, gives rise to a root-fibre, while the basal or proximal extrem- 

 ity gives origin to two or more fibres, one of which (the stronger) 

 appears to pass to the raphe. 



Other disperse motor clusters may probably be considered as 

 forming a part of the trigeminal motor system. 



The sensory roots can be traced with difficulty. Large gray 

 masses near the exit of the nerve, especially dorsally, are probably 

 the sources of some of the fibres. The cells are of a small variety 

 of the flask type. Some fibres were traced to the corpora posteria, 

 or large ganglion masses in front of the cerebellum. A large tract 

 leads into the peduncles of the cerebellum, thence to the median 

 radiating fibre tracts. In horizontal sections it seems that fibres 

 pass from the ventral longitudinal bundle to the fifth nerve, but of 

 this no absolute evidence was secured. (Compare Osborn, 

 "Amphibian Brain Studies," pp. 67-69.) 



(6.) The sixth nerves are very small and insignificant. The tracts 

 can be traced dorsad to the very floor of the ventricle, where is a 

 very inconspicuous nucleus, in essentials resembling that of the 

 third nerve. 



(7.) The facial nerve, if correctly identified, has a small definite 

 motor nucleus lying below the level of the fifth, and consisting of 

 fusiform and elongate pyramidal cells in a clustre, with the axis 

 directed toward the root. The position is ventrad and caudad to 

 the great nucleus of the fifth, and has a spindle shape. The cells 

 stain deeply, and the nucleus, while small, is remarkably promi- 

 nent and well isolated. The fibres have a direct course to the 

 root. The latter fact casts discredit upon the identification, and 

 suggests the possibility that we are dealing with a divergent mem- 

 ber of the trigeminal series. In that case the seventh roots were 

 not found, and the corresponding nucleus is absent, or is to be 

 sought in the cells about the lower part of the olives. In the latter 

 case the genu of the tract should have appeared in our different 

 consecutive series, as they were carefully examined with this in 

 mind. A dorsal root of the seventh was only provisionally identi- 

 fied as an ill-defined dorsal mass of flask-cells near the ventricle. 



(8.) The auditory nerve has two somewhat distinct but adjacent 



