84 
TUMOUR IN THE BRAIN OF A HORSE. 
was only to the left side—the one on whieh the brain was 
found to be affected. In addition to these symptoms, the 
animal gave indications of acute pain at intervals, and fre¬ 
quently pressed her head against the wall, apparently uncon¬ 
scious of surrounding objects. It appears, however, that her 
pulse did at no time rise so high as in the former case. 
On this occasion the left hemis[)here of the cerebrum only 
was sent for my inspection, but the structural alterations it 
had undergone, and upon which the symptoms and death of 
the mare evidently depended, so nearly resembled those ob¬ 
served in the same part of the brain of the former case, as to 
preclude the necessity of describing them in detail. The 
cause also which produced the lesions was the same as in the 
former instance, consisting essentially of the existence of a 
tumour about the size of a small heffs egg, which had im¬ 
bedded itself in the upper part of the posterior lobe of the 
left hemisphere of the cerebrum. For a description of the 
structural changes of the brain that had taken place in the 
former case, see page 712, vol. xxxv, of the Veterinarian for 
November, 1862. My reason for referring to these lesions 
is, that the description I have given of them strictly applies 
to those in the present case. 
The tumour, however, although of the same character, 
was evidently not developed precisely in the same manner. 
In describing the former case, I had no hesitation in stating 
that it arose from a bulging out, in a forward direction, of the 
anterior wall of the left lateral sinus, thus forming a sac, 
which was particularly evidenced by its smooth lining mem¬ 
brane being continuous with that of the right lateral, and also 
the superior longitudinal sinuses. The tumour in the present 
case, however, as far as I am able to cletermine, was only indi¬ 
rectly connected with tlie sinuses of the dura mater. Its 
inner surface is quite smooth and glistening, having all the 
character of a serous membrane; and I have no doubt was 
continuous with the inner coats of the veins. The tumour 
contained a large coagulum of blood, a part of which, judging 
from its condition, must have been in this situation for a 
long time. I am inclined to consider that the formation of 
the tumour was due to a varicose condition of one of the 
superficial veins of the cerebrum, near to its junction with 
the posterior extremity of the longitudinal sinus. In the 
former case the coat of the sac was thick and dense, but in 
the present one it was thin. It is interesting to observe 
that in neither of these cases was there anv evidence of 
loss of motive power, although in both the animals were 
unconscious. 
