THE SPINAL CORD.—GENERAL. 491 
confined to one side, though most pronounced on the side of the 
section. The same remark applies to motion. 
While there is considerable agreement as to the pyramidal 
tracts of the lateral column, the functions of the rest of these 
divisions of the cord are by no means well established. It is 
possible that vasomotor, respiratory, and probably other kinds 
of impulses, pass by portions of the lateral tracts other than 
the crossed pyramidal. When a lateral half of the cord is 
divided, the loss of function is not permanent in all instances, 
but has been recovered from without any regeneration of the 
divided fibers; and even when a section has been made higher 
up on the opposite side, partial recovery has again followed: 
so that it would appear that impulses had pursued a zigzag 
course in such cases. We do not think that such experiments 
show that impulses do not usually follow a definite course, but 
that the resources of nature are great, and that, when one tract 
is not available, another is taken. 
It is plain that impulses do not in any case travel by one 
and the same nerve-fiber throughout the cord, for the size of 
this organ does not permit of such a view being entertained ; 
at the same time there is a relation between the size of a cross- 
section of the cord at any one point and the number of nerves 
connected with it at that region. 
MQ 3QQ 
DvWit tt! v Wi 1 S0x0xigvilviVi VY IVIN TT vinVvovV Ivinn 1 
Sacral. Lumbar. Dorsal, Cervical. 
Fig. 348.—Diagram to illustrate relative and absolute extent of (1) gray matter, (2) white col- 
umns in successive sectional areas of spinal cord, and (3) sectional areas of several nerve- 
roots entering cord. NR, nerve-roots; AC, LC, PC, anterior, lateral, posterior columns ; 
Gr, gray matter (after Schafer, Ludwig, and Woroschiloff ). 
We may attempt to trace the paths of impulses in the cord 
somewhat as follows: 1. Volitional impulses decussate chiefly 
in the medulla oblongata, but also, to some extent, throughout 
the whole length of the spinal cord. They travel in the lateral 
columns (crossed pyramidal tracts chiefly, if not exclusively), 
and eventually reach the anterior roots of the nerves through 
the anterior gray cornua, passing to them, possibly, by the ante- 
‘ 
