AND ITS MEMBRANES IN THE HORSE. 591 
Such-like accidents being* familiarly known to veterinarians, 
1 need not adduce any facts in support of them: 1 shall there¬ 
fore pass on to the consideration of spontaneous lesions, which 
is the object of the present memoir. 
Congestions and sanguineous effusions, and inflammation of 
the spinal membranes and of the marrow itself, are the only 
spontaneous alterations that have come under my notice ; and 
these I shall consider in succession. 
Sanguineous Congestions in the Membranes are frequent 
enough among horses: they commonly happen between the 
pia mater and the arachnoides; sometimes in the tissue which 
unites the dura mater to the vertebrae; rarely within the spinal 
sheath. No precursory sig*n foretels their arrival, nor does any 
pathognomonic symptom betray their presence ; their commence¬ 
ment is sudden, and is instantly succeeded by marked derange¬ 
ment in the locomotive functions: the dorso-lumbar region being 
their ordinary seat, palsy of the hind limbs, more or less com¬ 
plete, becomes the consequence. 
These congestions, at length bursting, are sometimes fol¬ 
lowed by haemorrhages into the meninges of the marrow, 
which have by Doctor Ollivier been described under the name 
of hematorachis ; but whose existence can only be detected by 
examination after death. 
One easily conceives how these congestions and haemorrhages 
give origin to a number of disorders which it is impossible to 
particularize, so much do they depend upon the seat of these 
lesions, their extent, and especially the suddenness with which 
they have taken place. We know in effect that a very incon¬ 
siderable effusion of serum or blood taking place suddenly, on 
any portion of the membranes, is sufficient to produce at 
once decided paralysis; while a much larger quantity of the 
very same liquids, gradually effused, will at times occasion no 
important alteration, and often continues unsuspected until dis¬ 
covered after death. 
We have every reason to believe, that in horses the sangui¬ 
neous spinal congestions often precede inflammation of the 
spinal marrow and its membranes, in which case it becomes the 
occasional cause: the rapid advance of palsy of the hind limbs 
in this animal, and especially its sudden and almost instantaneous 
attack, leaves us no room to doubt that it is so, if not in a!J, at 
least in the majority of cases. 
It appears also highly probable that the spinal marrow of the 
horse is itself the occasional seat of sanguineous effusion or 
true apoplexy. The development of the organ, the impor¬ 
tant functions it performs, and the frequency of congestions of 
