TUMOUR IN THE LATERAL VENTRICLE. 
15 
removed in like manner, brought into sight a remarkable 
condition of the lateral ventricle of this side. It was found 
to contain what at first appeared to be a firm, membranous 
cyst, which not only filled it entirely, but caused a disten¬ 
sion of the walls of the cavity. Upon further examination, 
however, it proved to be a tumour, of considerable size, of a 
round oblong figure, much too large for the cavity of the 
ventricle in its normal state ; and the yielding of the sub¬ 
stance of the brain, and expansion of the cavity, were very 
conspicuous. The sides of the cavity were everywhere 
concave, and corresponded to the shape of the tumour; the 
septum lucidum was forced in the direction of the right 
ventricle, and not ruptured, so that each cavity was quite 
entire. The serous fluid was but little augmented within 
the left ventricle, but was of the same colour and character 
as that in the right. On a careful removal of the tumour, it 
was found to be an accumulation or deposit, of the same 
kind of earthy concretion as is occasionally found about the 
pineal gland. It was deposited between the membranous 
layers of the pia mater that invest the plexus choroides, and 
the first formation of the tumour evidently commenced 
within the plexus, and, as it enlarged, carried the mem¬ 
branous surface of the plexus with it, while the membrane 
became proportionately thickened with the increase of the 
tumour, and ultimately became a firm investment. Besides 
the lime-like substance, the tumour was composed of a 
cloudy, thick liquid, serving to enclose or surround uni¬ 
formly the hard substance, or what I took to be phosphate of 
lime principally. This cloudy liquid appeared to be the 
material from which the concrete substance was deposited ; 
and, in all probability, it would have been wholly converted 
into that substance, provided the horse had survived the 
necessary period. The tumour was of the shape of a kidney 
potato, and measured two inches and a half in length, and 
five inches in circumference. 
Observations .—Previous to making any remarks relative 
to this horse’s case, let us cursorily examine the structure of 
the brain and nervous system. I shall not put the ana¬ 
tomical acquirements of my readers to any inconvenience, or 
their memories much upon the stretch, to follow me through 
the brief description that I shall here give. First, we trace 
all the large nervous trunks, from the extremities and other 
parts of the body, to the spinal cord, and there we find them 
to arise by a double set of fibres, one from the superior 
columns of the cord, and the other from the inferior 
columns ; or, if it be preferred, from the anterior and pos- 
