594 ON THE DISEASES OF THE SPINAL CHORD, &G\ 
take place, not ill the pia mater, whose vessels are simply in¬ 
jected, but in the cellular tissue uniting that membrane to the 
arachnoid. Here, the eephalo-spinal fluid undergoes some re¬ 
markable changes: in some cases it loses its limpidity, and turns 
quite red; in others its place is supplied by a greater or smaller 
quantity of effused blood. I have never discovered any puru¬ 
lent matter, as is sometimes found in man. The rapid progress 
the disease makes in horses, is, no doubt, the sole cause of this 
difference. 
The spinal marrow itself \ as well as the membranes enve¬ 
loping it, is susceptible of inflammation. This phlegmasia, 
which is named myelitis , may invade the entire marrow, or only 
occupy some one of its regions. It gives origin to a series of 
symptoms which I shall not attempt a description of here, whose 
violence is greater the nearer the disease approaches the brain. 
The disease may be either acute or chronic: it rarely assumes 
the latter type in horses. I am acquainted but with one well- 
authenticated example, and that we owe to M. Dupuy. I have 
already noticed it. Acute myelitis, much more frequent, con¬ 
sists in a simple vascular injection of the marrow, giving the me¬ 
dullary substance a red-pointed appearance, and the grey sub¬ 
stance more or less of a rosy tint. Should the disease continue, 
this condition speedily changes: the marrow loses its consistence, 
becomes soft and spreads, and is converted into a kind of white 
or grey pulp, sometimes of a colour like wine, without any trace 
of primitive organization. These diseases spring up in horses 
with astonishing promptness: one, two, or three days, suffice for 
their production. The cases I shall relate will, I trust, remove 
all doubt on this head. 
Some authors, among w horn we must class M. Recamier, sup¬ 
pose that the softening of the marrow is not the effect of inflam¬ 
mation, but the result of a special alteration of the nervous sub¬ 
stance. M. Ollivier professes an altogether contrary opinion, 
upholding it by asserting that these softenings are almost always 
accompanied by inflammation of the surrounding tissue, and are 
more especially conspicuous in cervical and lumbar affections, 
parts in which the grey substance predominates ; and that, as 
everybody knows, is most vascular, and consequently most liable 
to inflammation. M. Andral is of the same opinion, without, 
however, denying the possibility of softening’s of an especial 
nature. The researches I have hitherto made, which I shall 
shortly produce, incline to the opinion of the last of these authors, 
and lead me to think that the softening of the spinal marrow in 
horses is almost always the work of inflammation. 
[To be continued.] 
