loo THE SPINAL CORD AND CEREBELLUM 



however, is the great crossed pyramidal tract stretch- 

 ing from the cerebral cortex to the large cells of the 

 anterior horn of the gray matter of the cord, which 

 serve to connect it with the anterior roots of the 

 spinal nerves and so with the muscles of the body 

 and limbs. The direct pyramidal tract is so called 

 because its fibres pass down the same side of the cord, 

 crossing, however, before they make their connection 

 with the anterior roots of the spinal nerves through 

 the cells of the ventral horn.* The median posterior 

 tract is composed chiefly of coarse fibres derived from 

 the posterior or dorsal root of the spinal nerves, which 

 to reach it pass through the external posterior tract 

 lying adjacent to it. This has been said to be the 

 chief path of sensory impulses to the brain, t but 

 all physiologists are not agreed on this point. The 

 posterior roots furnish other fibres, which pass inwards 

 to the vesicular cylinder! and other cells of the gray 

 matter. These are especially interesting, for although 

 forming part of the dorsal or sensory root, they lead 

 to cells which, as already stated, are not held to be 

 sensory in the ordinary acceptation of the term. The 

 fibres of the cerebellar tract take their origin in the 

 cells of the vesicular cylinder just mentioned, and 

 pass up the cord on the same side to the cerebellum.§ 

 It is said to begin rather suddenly at the level of the 

 second lumbar nerve. In addition to the above tract 

 the cerebellum by its supreior peduncle receives the 



* Foster, loo. cit., p. 962. t Ibid., p. 967. 



I Ibid., p. 950. § Ibid., pp. 962-964. 



