576 POPULAR LKCTURE ON THE PREVAILING EPIZOOTIC 
The present form of distemper, unlike the pustular one which 
preceded it, is neither infectious nor contagious. Its principal 
seat is in the organs of respiration, particularly the lungs, their 
covering, the lining of the ribs, and the membrane lining the 
numerous divisions of the windpipe which convey the air to the 
different parts of the lungs (lights) in breathing. The manner 
in which the lungs are affected is not similar to any other affec- 
tion hitherto known. The disease seems first to commence in 
the lining membrane of the air tubes and cells forming the greater 
bulk of the lungs. Inflammation is set up in this membrane, 
and, instead of its increased secretion being of a mucous charac- 
ter, such as man “spits” or “coughs up” when affected with a 
severe “cold,” it becomes changed to a plastic or adhesive cha- 
racter, being formed from that portion of the blood called itfc 
lymph, or the matter with which nature principally forms new 
parts, and repairs any losses that may occur to the frame. 
This lymph, when it becomes secreted in the air tubes and cells 
of the lungs, remains there, its adhesive or plastic qualities caus- 
ing it to adhere to the parts so very strongly, that the animal 
cannot expel it in the same manner by coughing, as she would 
dislodge an accumulation of mucus from the bronchia. 
Generally, only the lungs of one side of the chest are at first 
affected, if those of both sides are attacked at the same time, 
death shortly takes place from suffocation. Lymph becomes de- 
posited also in the other parts which I have mentioned as the seat 
of disease, especially the fabric of which the lungs are composed. 
In some cases the cavity of the chest, on one or both sides, is 
filled with water : when this happens, the case is almost hopeless. 
The exciting cause of all these changes, and of every epidemic 
or epizootic disease, appears to be connected with some peculiar 
state of the atmosphere. Yet, in what this peculiarity consists we 
have, in the present state of science, no means of deciding. We 
cannot, by the most minute analysis, detect the slightest difference, 
in the component parts of the air, in which we well know, from 
deductive reasoning, the subtle poison lurks, and of which, per- 
haps, man, with all his powers of investigation, even strengthened 
by future discoveries, will never be able to take cognizance, ex- 
cepting through the medium of the disastrous effects which it pro- 
duces, not alone on those animals which he has made subservient 
to his use by domestication, but also on himself. 
To some this may appear an object of wonder, when they con- 
sider the great and surprising discoveries that have been made in 
the science of chemistry. But is it more astonishing than the 
fact of the air of a chamber strongly impregnated with a perfume 
(musk, for example), of which we are made immediately aware by 
