138 MR. youatt’s VETERINARY 7 lectures. 
The Schneiderian membrane is the guard of the lungs, and it 
arrests every intruder. No part of [the frame has a more import¬ 
ant function to perform,—no part is endowed with greater sensi¬ 
bility,—no part is exposed to so much injury. The currents of 
air which are continually traversing it; the thousand extraneous 
bodies which are impinging upon it; the pungent and poisonous 
vapours which are coming so incessantly in contact with it; all 
are sources of irritation and debility, and we need not wonder 
that it is so disposed to inflammation, and that that inflammation 
will run its course. 
Alternations of Temperature. —Besides the injuries to which 
it is unavoidably exposed, there are others, and far more power¬ 
ful, artificially and absurdly introduced. I have adverted to 
them when speaking of coryza. Nothing could be so debilitating 
or so dispose this membrane to inflammation and all its conse¬ 
quences, as the sudden change of temperature to which this sen¬ 
sitive membrane used to be exposed, in that destructive system 
of stable management which once everywhere prevailed, and 
which is still maintained in too many establishments. The heat 
alone of the stable, without the sudden and excessive change, 
would wear out the vital power of the membrane, by the constant 
state of excitement it produced. 
Ammoniacal Vapours. —But, worse than this, and more con¬ 
nected with our subject (for these alternations of heat and cold 
are far more injurious to the lungs than to the membrane of the 
nose, and dispose more to pneumonia than to glanders,) there 
are the irritating pungent vapours which abound in every heated 
and closed stable. I have said that the lining membrane of the 
nostril, and the conjunctival membrane, are painfully irritated 
when we breathe but for a few minutes the atmosphere of these 
ill-managed stables. The horse breathes there all night and the 
greater part of the day. The injurious effect of these gases is 
spent on the pituitary membrane chiefly, or alone, with the ex¬ 
ception of the eye. By it the ammonia, so plentifully extricated, 
is arrested and absorbed. If the slightest portion of it reached 
even the larynx, violent, and so long as the stimulus was ap¬ 
plied incessant, cough would be excited. All the mischief which 
is done is inflicted on the conjunctival and Schneiderian 
membranes, disposing the one to the specific inflammation of 
ophthalmia, and the other to the inflammation of glanders, or 
supporting that inflammation when excited. The lungs are 
comparatively little or not at all affected. 
Often-respired Air and the Vapours of put ref ping Substances. 
There are also other changes going on in the air of the closed 
stable, not so deleterious as some have imagined, nor affecting 
