DISEASES OP THE RESPIRATORY ORGANS. 335 
of superficial vessels, especially when a cough is present, 
being a thing of frequent occurrence. 
Ultimately, disease of the mucous membrane may result 
in hypertrophy of the general structure, or of the epithelium 
only, and various forms of exudation, occasioning constriction 
or the formation of membranous bands. 
Affections of the parenchyma of the lung have especial 
reference to the vascular system, consisting, as they do, of 
disturbance of the circulatory function; such diseases as 
active determination of blood, congestion, and inflammation, 
belong to this class. The first-named disease is essentially 
local, and generally transient; its chief peculiarity is accele¬ 
ration of the respiratory movements, without a corresponding 
excitement of the general circulation, the bronchial murmur 
being audible over the w hole of the chest. In congestion 
the motion of the mass of blood is retarded or arrested, and 
hence the state of the pulse is at once indicative of the 
affection. Inflammation, although an active disturbance, is 
not often indicated by very energetic signs, and a tendency 
to assume the subacute form is almost constant. 
Diseases of the investing membrane of the lungs wdll 
occupy a considerable portion of our attention. Of the 
general character of the affections, it may suffice to say that 
most of the forms of derangement are of a passive nature, 
being indicated by slight, oftentimes almost imperceptible, 
symptoms, terminating in exudations of fibrinous fluid, 
and occasioning changes of such importance in the lungs 
as to render the animal unfit for active service, even if they 
do not immediately terminate his existence. 
We shall endeavour, from the evidence before us, to show 
the insidious nature of these affections, and the probability 
of their unsuspected existence for some time prior to the 
development of the symptoms, which are usually accepted 
as the signs of their commencement, but which, in reality, w e 
are persuaded are only presented wffien the disease has 
already made considerable progress. 
(To le continued^ 
