594 'Journal of Comparative Neurology and Psychology. 



roots by whose confluence the sensory root is formed. In the section 

 on the tegmentum occur the following paragraphs which bring for- 

 ward most important considerations for the interpretation of this 

 nerve root: "Even within the limits of the upper corp. bigem., the 

 central tubular gray matter encloses nuclei that give rise to the motor 

 nerve roots referred to, which lie more or less near the median line; 

 also a laterally disposed sensory nerve tract, the roots of the 5th cere- 

 bral nerve. The fibers composing these roots originate at the outer- 

 most border of the gray matter that surrounds the aqueduct of Sylvius, 

 in small collections of large bladder-shaped cells 60 microns in length 

 and 45-50 microns in breadth (Fig. 272 V), and form themselves by 

 degrees into a series of bundles whose transversely-cut surfaces, suc- 

 ceeding each other like the links of a chain (as seen in cross-sections 

 made in this region), lie in a curved line aroimd the outer edge of 

 the thick wall of gray substance which surrounds the aqueduct (Figs. 

 273 and 274, 5'). The cell masses from which spring the two kinds 

 of nerves, motor and sensory, have then, even in the region of which 

 we have been treating, the same general position in relation to each 

 other that they retain throughout the whole extent of the central 

 tubular gray matter, those connected with the motor nerves lying in 

 the neighborhood of the median line, and towards the anterior part 

 of the ring of gray substance, while those connected with the sensory 

 nerves are placed laterally and at the same time towards the posterior 

 part of the same ring, and the nerves of this region thus become 

 anatomically analogous to the anterior and posterior spinal nerves" 

 (p. 704-5). 



At the time that Meynert wrote, the origin of this root from a col- 

 lection of large cells in the locus coeruleus was not surprising, as 

 indeed all the other sensory roots were described as arising in certain 

 collections of cells. When later, as one of the results of the Golgi 

 silver technique, it was found that the motor nerves alone arose from 

 cells within the central nervous system while the sensory nerve fibers 

 arose from cells in the spinal and cranial ganglia, serious question 

 was raised as to the sensory character of this root. This aspect of 

 the case appealed especially to Kolliker and Van Gehuchten. Kol- 

 likor (1896) describes the origin of the bundle from a scattered 



