19G Report on the Patholor/ical Anatomy of Pleuro-pneumonia. 
and I think many of the facts enumerated show that this cannot 
be the case. 
In the attempt to trace each lesion to its exciting cause, I 
have, in every instance, been obliged to pass from the pleural 
surface towards the deeper parts. 
If the pleura were the starting-point of the disease, we ought 
to find the entire of the membrane, on one or other side of the 
chest, affected evenly throughout. Such is the common course 
of acute affections of the pleura, and the inflammation in this 
disease is generally of such an acute type that twenty-four hours 
would suffice for it to spread over the entire membrane. But I 
have invariably found that the pleural inflammation is either 
localised to the place where the lung is diseased, or is much 
more developed at that point. 
With such acute pleurisy as is often found, a case ought surely 
now and then to occur where intense fever and constitutional 
disturbance would lead to the early recognition of the disease, 
and call for the immediate slaughter of the beast ; and if the 
pleural inflammation were really the initial step in the disease, 
we might fairly expect occasionally to find a case in which 
pleurisy was the only part of the affection as yet developed. 
But this is not so. I have never seen, nor heard of a case in 
which pleurisy alone existed. The lung tissue is always diseased 
to some considerable depth. I have found, on the contrary, that 
the typical changes may occur in the lung, without any trace 
of pleural inflammation. 
In the common run of cases, where pleurisy is associated Avith 
extensive disease of the lung, the latter always gives the im- 
pression that it is of much older standing than the pleural 
affection. The pleurisy is commonly acute, while in the lung 
we usually have evidence of such chronic changes as would 
require a very long time for their development. From com- 
paring the lung lesions with the clinical history, I have often 
been forced to believe that the disease had existed for a very 
much h)nger time than was believed during the life of the 
animal. In one case, where the cow was described as having 
been in perfect health three days before I saw the lungs, and was 
said to have given nine quarts of good milk the day before, I 
found lesions in the lung, wliich, I think, must have taken at 
least six weeks for their production, associated with the first 
stage of intense pleuritis. Another cow, which was said to 
have been well, and milking five days before death, had a con- 
dition of lung which I cannot imagine could be developed under 
four or five months. Here there was also recent acute and 
extensive disease, engaging the entire of the left pleura. 
Tlie duration of the clinical history usually corresponds with 
