IRISH CENTRAL VETERINARY MEDICAL ASSOCIATION. 695 
while low-bred carriage- and cart-horses suffer most; the difference 
depends almost entirely on their diet; in the one case it is properly 
arranged and of a better quality, in the other it is just the opposite, 
in many instances an excessive feed at one time for the whole day. 
Broken wind is generally a result of other derangements, and in the 
earlier stages of many cases depends on functional derangement of 
the lungs, and not on emphysema. 
True pneumonia seldom ends in broken wind ; a peculiar fact, 
and not in accordance with the theory of ruptured air-cells. It 
generally comes on gradually, and is preceded by an attack of 
catarrh, chronic cough, or asthma, especially if the animal is ex¬ 
posed to such exciting causes as impure air or bad stable manage¬ 
ment, w^hile it is often known to come on without any symptom of 
respiratory derangement in horses fed on bad forage and allowed to 
gorge themselves. The result of this is to produce a debilitated 
condition of the stomach, in the first place from its over work, and 
in the second from its distension. Its walls become attenuated, its 
powers decreased, and its nervous influence participates in the 
general disturbance, while its functions become almost destroyed. 
It is the same nerve, the pneumogastric and its anastomoses, 
which supplies the stomach, diaphragm and bronchial tubes, 
and it is here I trace the connection. The whole course of the 
nerve becomes influenced, the inability extends, and the nervous 
force imperfect. The minute bronchi, as you are aware, are sup¬ 
plied with a distinct series of small muscular fibres, which dilate 
and contract the tubes at each inspiration and expiration ; and it is 
by their means that the respiratory action is properly carried on ; 
by cutting off their nervous force paralysis follows, and the tubes 
remain stationary to a certain extent, while the aid of the extra 
respiratory muscles has to be called on to remove the air from the 
cells and tubes of the lungs, and the performance of such produces 
the peculiar double action of broken wind. The cough which is 
usually the earliest symptom depends for its production on the 
increased bronchial secretion and the imperfect removal of it, 
giving rise to irritation. The breathing at first is only shortened ; 
but as the derangement continues, and the muscular fibres remain 
unused from their delicacy and minute structure they soon become 
atrophied, and perhaps ultimately absorbed, when the disease 
becomes incurable and the animal almost useless. On rapid exer¬ 
tion, the air is not removed or changed, and the unarterialized blood 
does not pass through the capillaries of the cell-walls as it should 
do, and passive congestion follows, producing the dyspnoea 
which the poor animal shows on being pressed to perform extra 
respiration. 
That the lungs of horses affected with broken wind are specifi¬ 
cally lighter, and said to be of a whiter colour, may depend on the 
same cause as the dilated bronchi, and distended air-cells must give 
such an effect. From a similar cause the diaphragm may become 
imperfect in its action, but as it is principally used as a respiratory 
muscle, I cannot attach much importance to it. 
XLii. 48 
