TUMOUR IN THE BRAIN OF A HORSE. 
711 
fissure. In doing this I observed that the anterior wall of 
the left lateral sinus apparently formed the tumour alluded 
to, which opinion was confirmed by following the course of 
the serous lining membrane of the superior longitudinal and 
right lateral sinuses into the interior of the sac. Some little 
care was necessary in dissecting the enlargement from the 
brain, in which, as before stated, it was not only partially 
imbedded, but also firmly adherent by its outer surface. The 
tumour itself extended as high as the torcula Herophili, and as 
low down as where this body joins the cavernous sinus at the 
base of the brain. After removing the tumour a considerable 
space was left in the posterior part of the hemisphere, 
covered, of course, by the pia mater and the arachnoidial mem¬ 
branes. On cutting through these membranes, which at 
this part were much increased in thickness and also extra 
vascular, a large cavity was exposed, the anterior part of 
which extended into the lateral ventricle. The surface of 
this cavity was of a darkish-yellow colour, and was covered 
with a cream-like matter, as far as consistence is concerned, 
but in colour like the substance it rested upon. The plexus 
choroides were but slightly altered from their normal state, 
excepting that they were a little enlarged from infiltration. 
On the surface of the descending cornu, near its commence¬ 
ment, numerous petechial spots of effused blood existed, and 
similar ones were also found on the surface of the corpus 
striatum, around which a slight tinge of a dirty red colour 
was observed. Such were the principal lesions noticed in 
the parts under consideration. 
Remarks .—The above case is highly interesting, both in a 
physiological and also in a pathological point of view. 
Perhaps more, and very likely better, explanations of the 
functions of the brain have depended upon observing the 
effects of pressure from tumours, &c., than upon any ex¬ 
periments founded on vivisection. If this is true, and I have 
reason to believe it to be so, we can make use of disease in 
studying the science of physiology. When this organ or any 
of its parts are functionally deranged, it should lead us first 
to the brain itself, and then, by the same aid, to the particular 
part of the organ that may happen to be functionally inter¬ 
fered with. 
Knowledge of this kind would also assist in conducting 
the mind to the proximate cause of the disease, which, 
although we might not be able to remove, nevertheless we 
should be in a better position to form a correct diagnosis of, and 
also to prognosticate with a greater degree of certainty what 
its ultimate result might be. Carrying out the ideas thus 
