336 PROGRESS OF VETERINARY SCIENCE AND ART. 
hold out as well that its proximate elements are morphologi- 
cally different from, any other vital structure of homologous 
or heterologous nature. 
It is clear from the antecedent, that in my usual attempt 
to trace the subject up through its various stages of deve- 
lopment to its present state, without dilating unnecessarily 
on collateral topics, I must treat many dogmatically, — the 
occasion will present itself for further discussion. But my 
object being to speak of the treatment of pleuro- pneumonia, 
I cannot omit further reflections on the nature of the disease. 
There are certain products of morbid action that are not 
the result of an accidental process, but are regulated in their 
formation by as complex a series of organic laws as the 
preservation of the integrity of structure and normal exercise 
of vital function. The products of inflammation are thus 
readily distinguished from any mechanical exudations, as well 
as from the materials accumulated in natural or artificial cavities 
by simple exosmosis. It is by the ulterior changes, whether 
retrograde or progressive, of materials separated from blood, 
that w r e can unmistakeably determine as to the nature of the 
process that led to their existence. Serum is the me- 
chanically separated fluid that fills the distended serum- 
cavities and bursal enlargements ; but when the properties of 
coagulation within the body, of cellular development, and vas- 
cularization are met wdth in the material exuded, there is no 
doubt as to the nature of the process giving rise to its exudation. 
Vascularization need not necessarily occur, and the cellular de- 
velopment may be checked and degenerate, but we have still 
abundant proof afforded that in inflammation alone such an 
exudation could occur. The solidified lymph that plugs the 
bronchial tubes, that gluts the interlobular tissues, wdth the in- 
flammatory globules and fibro-plastic cells that the microscope 
reveals in that lymph, never are formed in simple hyperaemia, 
or congestion due to lack of tonicity of the capillary vessels, 
which lack of tonicity, according to Schmelz, occurs in conse- 
quence of the depressing influence of the causes in operation, 
that act locally on the lungs as well as generally on the con- 
stitution, in lowering the vital powers of cattle affected w ith 
pleuro-pneumonia. I have seen some beautiful preparations 
by Hering of the lymph exuded in the bronchial tubes and 
air-vesicles forming perfect casts of lung tissue ; and w 7 e all 
know that plastic, coagulable lymph, is never seen on 
mucous surfaces except, and that rarely, in inflammation. 
There has not been any other specific process discovered 
w'hereby such casts can possibly be formed. 
Schmelz, whose remarks are published in the Repertorium 
