614 



MANUAL OF PHYSIOLOGY. 



These two great duties of the spinal marrow had better be 

 considered separately : 



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 



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/., Anterior median fis- 

 sure; p.m.f., Posterior median fissure; c.c., Central canal; s.r., Substantia 

 gelatinosa of Rolando; a.a., Funiculi of anterior root of a nerve ; p., Fnnic- 

 ulus 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. 



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 

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

 succeeding pair of roots a direct loss to its thicki 



