230 MR. youatt’s veterinary lectures. 
increased quantity of blood is hurried through these little vessels, 
for the vast expenditure of arterial blood in rapid progression 
must be provided for. These minutest of capillaries are sadly 
distended—irritated ; their contractile power is destroyed—in¬ 
flammation is produced—mechanical injury is effected—the ves¬ 
sels are raptured—blood is poured into the interstitial texture, 
—this increases the irritation,—intense inflammation and conges¬ 
tion, with all their train of fatal consequences, ensue. 
' Alternations of Heat and Cold. —The following are the most 
frequent causes of pneumonia. A sudden change from heat to 
cold,— the change from a warm stable to a colder one—the neglect 
of the usual clothing—the neglect even of some little comforts— 
riding far and fast against a cold wind, especially in snowy 
weather—loitering about when unusual perspiration lias been 
excited—loitering tediously bv the side of a covert on a chilly 
blowing morning : the experience of every day convinces us, that 
these are the usual causes of pneumonia. The thing is so 
plain, that I am almost ashamed to detain you for a moment 
about it. Can any one hesitate as to the effect of cold applied 
to the extensive surface of the skin—closing so many pores— 
determining so great a quantity of blood to other parts—causing 
disturbance every where, and especially in the pulmonary circula¬ 
tion,—in that part which, from the delicacy and complexity of its 
organization, and more especially from the injury it has received 
by our absurd and cruel management of the horse, is most of 
all subject to inflammation, and that of the intensest kind ? 
It has not unfrequently happened, that when horses have been 
turned out too early to grass, or without gradual preparation, 
pneumonia has supervened, and especially if other causes have 
assisted. Few horses are, under any management, so subject 
to pneumonia as they who, in poor condition, and without pre¬ 
paration, are turned into a salt-marsh. The Plumstead marshes 
below Woolwich are notorious for this. 
On the other hand, I can imagine that a sudden and consider¬ 
able change from cold to heat shall be followed by inflammation 
of the lungs. Many horses perish in the dealers' stables from 
this cause. The circulation is considerably quickened; more 
blood, and that more rapidly, is driven through the lungs, pre¬ 
viously disposed to take on inflammatory action ; yet even here 
the sudden removal from the heated stable to the cold air, for the 
purpose of examination, has much to do with the production of 
disease. But enough of the causes of pneumonia. 
Symptoms. —Whether it is the consequence of previous dis¬ 
ease of the respiratory passages, or inflammation first appears in 
the cellular texture of the lungs, pneumonia is usually ushered 
