166 
TUMOURS IN TIIE BRAIN. 
would produce similar symptoms ; this., however, has not been 
the rule, for at most there has only been an analogy between 
the cases. We have, indeed, all observed the existence of dis- 
ordered function in both the sensations and the muscular 
movements of the animals, although in different degrees. 
Some animals were calm and in a state of drowsiness ; others 
had a fit of vertigo. Some had a tendency to go forwards, 
and others to go backwards, or occasionally on one side, or in 
a circle. Some could not be made to go backwards, while 
others refused to advance. The symptoms were permanent, 
passing through various stages, with well-marked exacerba- 
tions, in some animals, but in others they were intermittent 
only. The lesions have often produced sudden death, while 
in other instances death has been very lingering. I know 
that, to a certain extent, these anomalies can be explained 
by the different complications of the lesions, for these may 
be only transient, or may vary in their intensity, as well as 
in their seat. But how are those great dissimilarities to be 
accounted for, which exist in the propensities that animals 
show of moving in directions which are diametrically opposite 
to each other? It has been said that compression of the 
corpora striata takes away the power of an animal to execute 
retrograde movements. If this be true, the leading symptom 
in the case I have just explained, as in all other analogous 
cases, w T ould be of'necessity the privation of this faculty; for 
in this instance, as well as in others, the compression was 
extreme, in consequence of the enormous development of the 
plexus choroides, and the great distension of the parietes of 
the ventricles by the superabundant serous fluid contained 
in their cavities. Rather than our attempting to uphold the 
physiological law, of which I have just spoken, it would be 
much better to say that the compression of the ventricular 
parietes excites various, and serious derangements in the 
several sensations, and in the muscular movements, and con- 
sequently, in the power of locomotion. It is not, however, b} r 
compression internally communicated to the brain-substance 
surrounding the ventricles, by whatever cause it may be 
produced, which necessarily leads to these functional derange- 
ments, for M. Renault has observed that pressure by an 
abnormal osseous projection produces defects in the move- 
ments of the animal, and often results in death. The giddi- 
ness of sheep and, oxen is likewise very frequently produced 
by hydatids lodged on the surface of the cerebrum. I have 
likewise seen a case of giddiness in a horse which had a large 
cyst connected with the dura mater, and situated upon the 
exterior of the cerebrum. 
