DIMINUTION OF SENSIBILITY. 
305 
cranial cavity. Thus we account for the stupidity or insensi- 
bility which is one of the diagnostic symptoms of cerebral con- 
gestion or apoplexy, staggers as it continues inconsistently to be 
called in our nosology. The circulation through the brain is 
impeded — the supply of arterial blood which is necessary for the 
discharge of every function, and most of all for those of the 
sensorial system, is diminished or for awhile suspended, and utter 
unconsciousness is the immediate and necessary result. Or effu- 
sion takes place within the cranial cavity, and a similar effect is 
produced. It is thus that we account for the frequency of amaurosis 
as a consequence of staggers produced by over distention of 
the stomach, and determination of blood to the brain, or impedi- 
ment to its return, and by means of which it presses, in some cases 
at least, on the nerve of vision. It is thus, that by introducing a 
more regular system of feeding, that simple instrument the nose- 
bag saves the lives of thousands of horses every year, and, in fact, 
has exterminated one of the most destructive pests — an epidemic 
one as it used to be thought — of the equine race. 
Hydatids in the Brain. — It is on a similar principle, — the 
pressure on the brain, and its influence on the intellect, and on 
general sensibility, — that the sturdied sheep, or the animal in 
whose cranium an hydatid has taken up its residence, is languid 
and stupid, and goes staggering about, lost in his fit of musing, 
and wastes rapidly away, and dies a perfect skeleton. 
It is thus that the ox or the cow, infected by the same parasite, 
goes stupidly round and round, the food neglected, and rumina- 
tion having ceased, and she also pining quickly away. 
Hydatids in the Brain of the Horse. — A somewhat different 
account is given of the ravages of the hydatid in the brain of a 
horse. He had been observed for eight days to be apparently 
lazy, and perfectly insensible to blows — he would not draw at all, 
but stood stupid an^ careless about every thing; when, being 
forced by dint of threats to trot, although at the most gentle 
pace, he suddenly fell as if struck by lightning, and, recovering 
himself soon afterwards, shewed symptoms of the most violent 
phrenzy. After death an hydatid as large as a billiard ball 
was found pressing upon the left lobe of the brain*. 
Hydatids in the Spinal Cord. — It is thus when the hydatid 
finds its way into the spinal canal of the sheep, and there collects 
to itself groups of its own species, and lies between the dura 
mater and the arachnoid membrane, or in contact with the cord 
itself, and furrows its surface and renders it irregular and covered 
with false membranes, that, by impeding the circulation, and 
* Journal Prat, xxvi, 531. 
