598 DISEASES OF THE RESPIRATORY ORGANS. 
bronchial tubes may exist to such an extent that the slight¬ 
est stimulus, the contact of cool air, the presence of a par¬ 
ticle of food in the fauces, the membrane’s own secretion, or 
any external pressure, will suffice to produce the peculiar 
convulsive effort of expiration which constitutes a cough. That 
the larynx is the part most prominently coneerned, we have 
ample proof in our own experience, although the sensation 
of irritation is often felt in the Dronchial tubes. The occur¬ 
rence of cough is direct evidence of this state of irritability. 
The absence of cough is no evidence of the healthy condition 
of the membrane of larynx or bronchiae, as inflammation 
even may exist without it, and certainly increased secretion, 
evidenced by the mucous rale, is observed in many cases 
where cough is entirely absent. No stage of the disease can 
be said to be distinguished in a particular manner by cough ; 
it may be present from the first, it may only commence 
when the mucous secretion has become excessive, and it may 
not appear until the animal is eonvalescent; but in whatever 
stage it occurs, it must be considered as indicative of ex¬ 
cited sensibility, irrespective of the state of the diseased 
parts. 
Between catarrhal disease and inflammation, the difference 
is not so marked as to be easily defined; speaking of 
the local changes, it would be impossible to distinguish 
between the two in many instances; but certain consti¬ 
tutional effects follow upon the development of the more 
active disturbance, and enable us to say wdien the inflamma¬ 
tory condition is established, although they do not assist us 
to determine precisely when it commenced. 
An exacerbation of fever will generally be accepted as one 
symptom ; quickened respiration, certain evidence afforded 
by auscultation, and the character of the pulse, will further 
aid the diagnosis. The pulse will not, however, taken alone, 
suffice to distinguish the precise nature of the disease; a 
pulse of inflammation does not exist in practice. No evi¬ 
dence afforded by the animal body under disease is more 
difficult to w^igh impartially, none upon occasion so contra¬ 
dictory. Very slight causes we have found to produce 
remarkable effects, altogether disproportioned to the extent 
of the influence at work. And he who has not read the 
symptom carefully, and in the light of long experience, had 
best follow the example of some practitioners of talent and 
observation he could name, and disregard it altogether. 
Catarrhal diseases, when the blood is charged with debris 
from non-elimination, are, for obvious reasons, likely to 
assume a grave character. To illustrate our meaning, and at 
