OF DENISON UNIVKRSITV. 6 1 



and the entire higher portions, afford opportunity to trace the connec- 

 tions of the structures already described with the cerebral ganglia. 



Nuclei and tracts of the higher portion of the medulla and c rural 

 region, as seen in horizontal sections. 



The bladder cells of the dorsal root of the trigeminus. These remark- 

 able cells have already been referred to. They seem to have been first 

 recognized by Stilling, who regarded them as forming an accessory 

 nucleus of the fourth nerve, in whose tract they nearly lie. Stieda 

 (Zeitschrift f. wiss Zoologie, Band XX, ) falls into a worse error, re- 

 garding these cells as the true nucleus of the fourth, and failing to 

 discover the tract extending from the root cephalad, {Loc cit. Plate 

 XX, Fig 44.) Stieda's drawing is exceedingly conventional, so far as 

 concerns cells and nuclei. 



Meynert (Striker's Histology, Am. Ed., p. 705,) describes the 

 cells in question as follows : 



"The cells from which spring the above mentioned roots of the 

 fifth pair, differ strikingly, in regard to their shape, from the cells in 

 the common nucleus of the oculo-motor and trochlearis. The former 

 are inflated, bladder like, and furnished with but few and slender j*ro- 

 cesses, which project abruptly from the cells like a straw from a soap 

 bubble. The latter are large, like the former, but slender, and rich in 

 processes whose calibre passes by gradual transition into that of the 

 cells. The former resemble the cells of the spinal ganglia, the latter 

 those of the anterior cornua of the spinal cord." 



" Even within the limits of the upper corpora bigemina, the cen- 

 tral tubular gray matter encloses the nuclei which give rise to the motor 

 nerve roots referred to (oculo motor, etc.), which lie more or less near 

 the median line ; also a laterally disposed sensory nerve tract, the roots 

 of the fifth cranial nerve. The fibres composing the.se roots originate 

 at the outermost border of the gray matter which surrounds the aque- 

 duct of Sylvius in small collections of large bladder-shaped cells 60 

 micr. in length and 45-50 micr. in breadth." 



In Ar'ctomys the disparity in size between the cells of the nuclei 

 of the fourth nerve and these bladder cells forbids comparison, other- 

 wise the remarks quoted ajiply substantially. The deduction which 

 Meynert attempts to draw regarding the relative jxjsiiion of sensory 

 and motor nuclei in the medulla seems forced in this case, being based 

 on the pure assumption that these cells are sensory, while the differ- 



