THOUGHTS ON BROKEN WIND. 
59 
act of expiration : in fact, the animal shews all the symptoms 
characterised by the term broken wind. How is this to be 
explained] The last recognised symptom, namely the heaving 
in the flanks in expiration, is evidently only the last link in the 
chain of a disease situated elsewhere, and probably originating 
in the stomach. Now, if this animal were killed, we should 
most likely find an emphysematous state of lung (but not in¬ 
variably so, as we might discover many other morbid lesions 
instead of it). Supposing we do find it, are we to infer that the 
emphysema is the cause which produced this difficulty in the 
act of expiration, or that the difficulty of expiration, and the 
great action of the abdominal muscles, have produced the em¬ 
physema] This is a difficult matter to decide. If we consider 
emphysema as the cause, I think it can only be said to be so se¬ 
condarily. In any case, I would say that diseased action of some 
kind, evidenced by the cough, &c., preceded the symptoms of 
heaving at the flank, or broken wind, for some considerable period, 
and that emphysema would therefore, in the first instance, be 
an effect of a certain diseased action. I think we can hardly 
imagine that an emphysematous state of lungs preceded the 
attack of indigestion and chronic cough. Let us speculate for 
a moment on the nature of this emphysema. How can it be 
brought about ] This, again, is most difficult to determine. May 
it possibly consist in a diseased condition of the blood under 
which air is issued into the substance of the lungs at various 
parts ] In favour of such a notion, we know that it is very diffi¬ 
cult to empty these emphysematous sacs. Direct pressure of 
the finger will scarcely effect it; and, once emptied, you can 
never fill them to the same extent by forcing air into the lungs; 
indeed, we shall scarcely succeed perhaps in getting any air at 
all into them, tending to shew that they are not in absolute 
connexion with the air-cells. In what other way may the em¬ 
physema be produced! We must conjecture again. Supposing 
the bronchi to be in a low state of inflammation, as evidenced 
by the peculiar cough, this would be attended at first with tur- 
gescence of membrane and extra secretion of mucus. The vio¬ 
lence of the cough, or the absolute difficulty of expiration, owing 
to the inflamed and thickened state of the membranes (if we 
suppose the emphysema to precede the difficulty of breathing), 
forces the air through the passages, which are smaller in dia¬ 
meter than in health, and obstructed with mucus and weakened 
by disease; and, in the resistance the air meets with, the deli¬ 
cate walls of the air-cells may burst, and allow the air to escape 
into the parenchyma : this is a slow and gradual process, and 
the difficulty of breathing comes on imperceptibly. The same 
cause being frequently repeated will increase the mischief. The 
