TUMOUR IN THE BRAIN OF A HORSE. 713 
cranial cavity, but instead of pressing upon the cerebrum its 
effects were upon the cerebellum, a large portion of which 
had become absorbed by the pressure it had imparted. 
Now in this case there was at first partial paralysis of mus¬ 
cular power, which eventually became so general that the 
horse was obliged to be destroyed. On the other hand, in 
Mr. TolPs case muscular paralysis was not present, but 
volition was partially destroyed, as was evidenced by the symp¬ 
toms exhibited by the animal. If it be asked, “ what can 
the formation of the tumour be attributed to?” I would 
reply that the question cannot be answered so positively as 
could be wished, and to attempt it, even conjecturally, would, 
in my opinion, tax the ingenuity of the pathological anato¬ 
mist. That its development was very slow is indicated by 
the loss of brain substance—the whole of the gray, with a 
portion of the white fibrous part beneath it, was removed by 
absorption—and also by the character of the tumour itself. 
Even the coagula of blood in the interior of the tumour 
were evidently of long standing, which was especially indi¬ 
cated by their stratified appearance—these strata being alter¬ 
nately light and dark coloured. Their edges also were 
rounded, and many of them partially broken up. 
We might advance several theories from the arrestation of 
the blood in this sinus leading to the bulging out of the 
cavity anteriorly, so as to form a sort of sac, without any of 
them being the right one. I therefore prefer to leave the ques¬ 
tion of the original cause of the formation of the tumour an open 
one; but it having taken place, it is comparatively easy to 
understand how the blood, after being partially arrested in 
the sinus, could coagulate, even in several portions, each of 
which would gradually become larger, by the surfaces being 
continually bathed by blood in its passage through the 
sinus. I can conceive that in this way the tumour gra¬ 
dually increased in size until it assumed its full magnitude, 
while its pressure upon the cerebrum would account for the 
loss of structure of that organ, and which, like the forma¬ 
tion of the tumour, was a very slow process. I have no 
doubt that the structural disease thus produced had long- 
affected the volitional powers of the horse, but not to 
an extent to be detected by an ordinary observer, until about 
the 6th of September, when the waggoner first noticed some¬ 
thing wrong with the animal, which was attributed by him to 
exposure to wet and cold. I think it probable that this 
exposure had something to do in hastening the development 
of the acute symptoms, but none whatever in the production 
of the tumour. 
