THE SPINAL CORD.—GENERAL. 489 
cells are to be referred to the posterior gray cornua of the cord, 
which they connect in all probability with the cerebellum. 
7% Columns of Burdach (postero-lateral columns). — This 
tract is connected with the restiform bodies and reaches the 
cerebellum by the inferior peduncles. Secondary degenera- 
tions do not occur in these fasciculi, so that it seems likely that 
they connect nerve-cells at different levels in the cord; and 
they may also connect the posterior gray cornua with the cere- 
bellum as 6. 
Columns of Goll (postero-median columns).—They do not 
extend beyond the lower dorsal or upper lumbar region; and 
their fibers pass to the funiculi graciles of the medulla. As- 
cending degeneration follows section of these columns, 
The degenerations referred to above are visible by the 
microscope, and of the character following section of nerves. 
It is probable that they are the later stages of a primary mo- 
lecular derangement in consequence of interference with that 
continuous functional connection between all parts on which 
what has been called nutrition, but which we have shown is 
but a phase of a complex metabolism, depends. 
Decussation.—Sections of the cord, when confined to one lat- 
eral half, are followed by paralysis on the same side and loss of 
sensation, confined chiefly to the opposite half of the body be- 
low the point of section. The results of experiment, patho- 
logical investigation, etc., have rendered it clear that—1. The 
great majority of the fibers passing between the periphery and 
the brain decussate somewhere in the centers. 2. Afferent 
fibers cross almost directly but also to some extent along the 
whole length of the cord from their point of entrance, the 
decussation being, however, completed before the medulla is 
passed. 3. Motor or efferent fibers decussate chiefly in the 
medulla, though crossing is continued some distance down the 
cord, such latter fibers being but a small portion of the whole. 
This fact is best established, perhaps, by noting the results of 
brain-lesions. With few exceptions, susceptible of explanation, 
a lesion of one side of the cerebrum is followed by loss of motion 
of the opposite side of the body. These are all central, well- 
established truths. It is also now pretty well determined that 
voluntary motor impulses descend by the pyramidal tracts, 
both the direct and the crossed. That the posterior columns of 
the cord are in some way concerned with sensory impulses 
there is no doubt; but when an attempt is made to decide 
details, great difficulties are encountered. Experiments on 
