THE SPINAL CORD.— GENERAL. 471 



they may also connect the posterior gray comua with the cere- 

 bellum as 6. 



Columns of Goll (postero-median columns). — They do not 

 extend beyond the lower dorsal or upper lumber region ; and 

 their fibers pass to the funiculi graciles of the medulla. Ascend- 

 ing degeneration follows section of these columns. 



The degenerations referred to above are visible by the micro- 

 scope, and of the character following section of nerves. It is 

 probable that they are the later stages of a primary molecular 

 derangement in consequence of interference with that continu- 

 ous 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- 

 teral 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. 3. 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 chiefiy 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. 

 A^ith few exceptions, susceptible of explanation, a lesion of one 

 side of the cerebrum is followed by loss of motion of the oppo- 

 site 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 animals are of necessity very 

 unsatisfactory in such a case, from the difficulty experienced in 

 ascertaining their sensatipns at any time, and especially when 

 disordered. 



Pathological. — A good deal of stress has been laid upon 

 the teachings of locomotor ataxia in the human subject. The 

 symptoms of this disease are found associated with lesions of 



