62 BULLETIN OF THE LABORATORIES 



ences between any known sensory cells and those in question are cer- 

 tainly as striking as their resemblance. 



Similar cells have been described by Belonci, in birds, Stieda in 

 the turtle, and Herrick, in the alligator. x\s a matter of fact, no sub- 

 stantial basis exists for determining the function of these cells. Their 

 similarity to Purkinje's cells of the cerebellum gives some force to the 

 suggestion that there may be similarity in function if not in origin, 

 though the resemblance is still greater to the cells of the ganglion of 



Gasser. 



These bladder cells are especially well seen in the horizontal sec- 

 tions passing through the nuclei of the third and fourth cranial nerves. 

 (Plate XIX, Fig. 2, Be. Bc\ Fig. 4, b.) 



These cells are .05-. 07 mm. in diameter and of a baloon or flask 

 shape or polyhedral. The processes are few, and abrupt, and give rise 

 to a very large fibre. Such cells are first encountered in the base of 

 the tectum opticum, near the highest part of the nates and are sparsely 

 scattered in the tract which passes in a gentle curve laterad and caudad 

 and at the same time, somewhat ventrad, to form a disperse tract about 

 the aqueduct and thence caudad to the anterior part of the fourth 

 ventricle. Here the cells are most numerous and lie peripheral to the 

 strong motor nucleus of the fifth, which lies near the ventricle. Al- 

 though the two sorts of cells commingle in places, there is never any 

 difficulty in distinguishing them. The general relation is always that 

 described. The tract can be traced laterad and ventrad and the nu- 

 cleus itself describes a strong lateral curve at the point of departure of 

 the root tract, while scattered cells of this type can be traced to the 

 point where the fibres are lost in the common root of the fifth. 



Motor nuclei of the trigeminus. The cephalad portion of the tri- 

 geminal motor system is quite complicated. The highest recognizable 

 portion is the elongate cluster bordering the caudad portion of the 

 aqueduct and the cephalad part of the fourth ventricle. The cells are 

 figured, (Plate XIX, Fig. 4, a,) and are of the usual motor type, 

 measuring .05-. 06 mm. in length, by .02-. 02 5 mm. in width. The 

 prevailing direction of the principal processes is caudad, i. e. toward 

 the root, the opposite extremity being multipolar. 



A second nucleus lies ventro-laterad from this one and appears in 

 horizontal sections through the highest portion of the root of the fifth. 

 It lies nearly opposite the caudad part of the prepedunculus cerebelli 

 and is of circular outline and about fifty cells lie in one horizontal 



