629 
CONGESTION OF BLOOD IN THE BRAIN. 
sclsj and within and about the sheaths of all the nerves, and 
the base of the brain generally, cannot be mistaken, and may be 
compressible to a very considerable extent. I can see the utility 
and the necessity of this when I recollect the great quantity of 
blood which permeates the brain in a state of health, and which 
is so liable to be increased by many accidental circumstances. 
The structure of the longitudinal sinus, and the bands by which 
it is connected with the pia mater, force on me the probability, 
or rather the actual existence, of occasional dilatation and con¬ 
traction ; and the cellular substance about the rete mirabile was 
placed there, by its yielding resistance to guard these important 
vessels. While, therefore, I could account for all the symptoms 
of apoplexy on the principle of the supposed incompressibility of 
the brain—while I could imagine that the presence of a little 
more blood in the arterial vessels would render the venous ones 
impervious ; or the loitering of the blood in the veins would close 
the arterial vessels, and thus prevent the circulation of the blood 
through the brain, or produce injurious pressure on the nervous 
origins (for the rupture of a vessel and the extravasation of but 
a small portion of blood would be followed by very serious ef¬ 
fects) yet the inspection of various brains of horses that have 
died of staggers, or phrenitis, has forced on me the fact, that a 
considerably greater quantity of blood is sometimes found in the 
cranial cavity than at other times; and therefore the next class 
of diseases which I shall notice will fall under the head of 
Congestion of Blood in the Brain. 
Not necessarily connected with Inflammation. If I ride a ple¬ 
thoric horse far and fast, and especially on a warm day, I shall 
probably have congestion of the lungs without inflammation of 
those organs. They, and the respiratory apparatus generally, are 
over-worked in supplying the arterial blood which this excessive 
and unusual muscular exertion requires; and at length become 
so exhausted, that they can no longer contract on the blood which 
they contain. The horse is blown . Give a little time for rest 
and reaction ; hasten that reaction by proper stimulants, and the 
vessels gradually relieve themselves of the load which oppressed 
them : but, hurry the animal after he has exhibited symptoms of 
distress, or complete the exhaustion by immediate and unskilful 
bleeding, and he dies, and affords you a specimen, pregnant with 
instruction, of most extensive congestion, independent of inflam¬ 
mation. So, occasionally, when we ride a fat and pursive horse 
a little beyond his usual speed, he evinces temporary distress 
clearly not referrible to the respiratory system : he suddenly 
staggers, and threatens to fall. We have caused the blood to flow' 
