614 



MANUAL OF PHYSIOLOGY. 



I. SPINAL CORD AS A CONDUCTOR. 



From the anatomical investigation it may be seen that there 

 must be some special method of conducting impulses along the 

 spinal marrow, and that it is not merely a collection of the nerves 

 or an aggregation of the fibres that spring from it. In the first 

 place, these nerves, if all bundled together, would be much larger 

 than the cord, even at its thickest part; and, further, it does not 



FIG. 240. 



pm.f 



Diagram illustrating the course probably taken by the fibres of the nerve roots on 

 entering the spinal cord. (Schafer.) a.m.f., Anterior median fissure; p.m.f., Posterior 

 median fissure; c.c., Central canal; s.r., Substantia gelatinosa of Rolando; a.a., Fuuic- 

 uli of anterior root of a nerve; p, Funiculus of posterior root of a nerve. By following 

 the fibres, 1, 2, 3, etc., their course through the gray matter of the spinal cord may be 

 traced. 



taper evenly toward its lower extremity, as it should were each 

 succeeding pair of roots a direct loss to its thickness. 



The posterior roots of the spinal nerves pass through the white 

 substance to reach the posterior gray column, where they break 

 up into numerous fine twigs, which are distributed to neighboring 

 parts of the gray network of fibrils, in which they are lost with- 



