THE PYRAMIDAL TRACT 



517 



-V 



•fa 





"■X 



gK. 





c.p. 



feM 



^y-^ 



.y 



^1 





-.— p,t. 



-=, y 





c.c. 



Fig. 2 From the seventh cervical segment of the spinal cord of the guinea- 

 pig. Pyridine-silver stain. X 80. The pyramidal tract is located in the ventral 

 part of the posterior funiculus. It is darkly stained because it is composed 

 chiefly of non-medullated and fine meduUated fibers. It is not as compact as 

 in the rat, since there are scattered through it large medullated fibers belonging 

 to the cuneate fasciculus. This is especially evident in the posterior part of the 

 tract, where it appears as bundles of fine fibers in the ventral part of the cuneate 

 fasciculus. The fibers of the pyramidal tract are more densely grouped ventrally 

 and laterally near the gray substance and this gives the cross section of the two 

 tracts somewhat the form of the letter V. 



As seen in figure 2, tlie tract is composed of irregular groups of 

 axons which are closely grouped near the posterior horns and the 

 transverse portion of the gray substance, while medially and 

 posteriorly they are more widely separated. The axons were 

 not as numerous as in the rat but were of about the same di- 



