Section Iv. of the Spinal Cord.

From the continuity and identity of structures, the spinal cord is subject to essentially the same diseases as those of the brain.

1. The Membranes.

=Inflammation= of the latter may exist alone, or in connection with that of the membranes of the brain, constituting cerebro-spinal meningitis. Inflammation of the dura mater is an uncommon occurrence. The inflammation in spinal meningitis is almost wholly confined to the pia mater, this being the more vascular of the membranes. A pale reddish, or sometimes purple color, with a bloody jelly-like infiltration, characterizes the earlier stage, while at a later period the membrane presents a greyish or dirty yellow appearance, from the presence of a thick pus-like substance covering the surface. Such inflammations may be either idiopathic, rheumatic or traumatic in their origin.

In spotted fever the inflammation extends to the pia mater of the base of the brain, and is remarkable from the epidemic form which it sometimes assumes.

=Tubercular= deposits, as well as tumors of various kinds, may be found connected with the spinal membranes, so similar to those described with the cerebral membranes, as not to require separate notice.

=Serous effusion= may be found in the spinal canal, in the same cases when it exists in the cranial cavity, and may be either a diffusion of fluid through the sub-arachnoid space, that has been effused in the brain, or it may originate from the membranes of the cord itself. The fluid may be either between the vertebræ and dura mater, or between the latter and the pia mater.

A peculiar form of dropsy of the spine is sometimes found, congenital in its nature, and accompanied with a deficiency in the spinal column, by means of which a cleft remains in the arch of one or more of the vertebræ; hence the name, Spina bifida, as applied to this disease. The effusion in these cases, taking place before the vertebræ are fully developed, the pressure from within prevents the final closure of the canal posteriorly; when, from want of support at that point, the membranes and covering tissues, yielding to the pressure from the accumulating fluid, gradually protrude at that point, producing a rounded fluctuating tumor. The disease is more frequently found in the lumbar region, although it may occur in the dorsal or cervical, and in some cases may involve the whole spinal column.

2. Spinal Marrow.

=Inflammation= of this structure, (myelitis,) presents the same character, and may be followed by the same results as inflammation of the brain. From the distension and engorgement of the capillaries of the inflamed part, a bright red color may be presented, not only on the surface, but in the substance of the cord when exposed by division. Blood may also be found effused in the substance of the cord, or between its membranes, or between the bony walls and the dura mater.

=Softening= of the spinal cord, may arise either spontaneously, or as a consequence of injury. When spontaneously taking place, a large portion of the cord may be involved. The appearance presented, is most usually that of a soft pulpy mass, which easily breaks down upon the opening of the membranes. When the result of injury, the softening is generally confined to the portion involved in the original violence.

=Hardening= of the spinal marrow, (sclerosis,) may be one of the results of inflammation, yet the accompanying symptoms may vary so slightly from those of other forms of spinal disease, that the post-mortem alone, will disclose the true nature of the difficulty. In locomotor ataxy, the posterior columns of the cord are usually affected with this change.

=Atrophy= of the spinal cord, differs from hardening, in the shrinking which attends the progress of the disease, although there may be increased density, as in the former case. The essential peculiarity of atrophy, consists in an increased development of the fibrous elements of the cord, which by pressure, gradually destroys the elementary nerve constituents. This disease is confined chiefly to men of a middle age, and is generally the result of venereal excesses; muscular over-exertion, exposure to cold, &c., may also be exciting causes.

=Morbid Growths=, of various kinds, and closely resembling those found in the brain, as well as animal parasites, are sometimes found in the spinal cord.