596 WEST OF SCOTLAND VETERINARY ASSOCIATION* 
the corpula striata, in connexion with other parts of the 
medulla oblongata, is the centre of volition* It the corpora 
striata be the centre of voluntary movements, how reasonable 
is it to suppose that a tumour pressing upon its surface will 
dissociate its unexplainable regulatory agency and thereby 
cause the framework, over which its office is to preside, to 
perform irregular movements which we term staggering ? 
c4 4thly. The animal carries the head towards the right side, 
inclines to turn the body towards the left , and has a peculiar 
jerking action of the near fore extremity. If I blindfold a 
pigeon over the right eye, it always turns towards the left; 
irritate the corpora quadrigemina, and jerking or convulsive 
actions are induced ; and destroy or sufficiently injure the left 
quadrigeminal tubercle, and not only have you this convulsive 
action, but likewise the animal will perform a circulatory or 
vertiginous movement towards the left side. Here then is 
sufficient to satisfy the most inquisitive. The animal in 
question was blind in the right eye, and, like the blindfolded 
pigeon, she wheeled towards the left. The left quadrigeminal 
tubercle* from compression, was organically affected and 
functionally deranged, and hence, as in the above case, the 
cow had not only convulsive actions of the left fore extremity, 
but also turned towards the left , that being the side on which 
the injured quadrigeminal tubercle was situated. 
44 And now bear with me while I attempt to explain the last 
symptom of importance, viz., the paralysis of the right optic 
nerve. At the first glance it will appear strange that we 
should have the diseased action located in the right eye, 
while the cause of disease and the lesion resulting therefrom 
are situated on the left side of the brain ; but, as I said 
before, a correct physiological knowledge of the brain will 
account for the most hidden and mysterious symptom, and 
even so here do we find it* 
44 The optic nerves, from their deep origin in the quadrige- 
minal tubercles, optic thalami, and corpora geniculata, pass 
to the base of the brain, and at their anterior boundary of 
the interpeduncular space decussate, the fibres of the one 
passing on to the fibres of the other, after which they run 
forward and enter their respective eyes, in the interior of 
which they expand to form the retina, the reflection of light 
upon which constitutes vision. 
44 A tumour situated upon any one part of the course of 
these nerves must of necessity prove injurious to vision, and 
hence we find that a tumour situated in either lateral ventri- 
cle is as perfectly able to destroy vision, being in contact 
with the thalami optici (upon which the sensation of vision 
depends), as if it had been situated in the anterior chamber 
