808 WEST OF ENGLAND VETERINARY MEDICAL ASSOCIATION. 
set on the fact of the nerve being pretty closely applied to the posterior 
aorta, or, as some have it, its holding that vessel, as it were, in a sling, 
and consequently any inordinate traction on the nerve during violent 
pulsations puts it on the stretch, and by such means sufficient injury in- 
llicted to render it unable any longer to perform its proper office. But 
some may say that if we accept this theory it is next akin to asserting 
that Nature is a bungler in so arranging structures that they are liable 
to become injured during exertion, &c.; but I, for one, do not consider 
such to be, if urged, a very weighty objection. The probabilities are, I 
think, that horses were not destined for such inordinate work as we often 
require of them, and that it is in consequence of this unnatural physical 
exertion which we compel them to undergo that disease is induced ; and 
why should it not occur in this nerve as in other structures entering into 
the formation of the body? Thus much for mechanical injury brought 
about by extraordinary pulsations consequent on fright or over-exertion. 
Then, again, with regard to “ roaring” following acute affections attended 
with general fever, as, for instance, influenza, pneumonia, pleurisy, laryn¬ 
gitis, &c, &c. 
Now, in each one of these febrile disorders the increase of animal heat 
is very marked; next to this increase of heat is increase of involuntary 
motion, motion of respiration, motion of circulation. This increase of 
speed in these two grand sets of muscles, the prime movers of the whole 
body, immediately causes increased pulsations, both in tension and rapidity 
of stroke. 
Is it feasible that the nerve becomes Impaired by the unusual action of 
the heart under these circumstances, or is the injury consequent on its 
connection with the lungs through the pulmonary plexi already spoken 
of, which organs are equally excited with the heart ? Whichever of these 
it may be I must be content to leave to you, asking for your individual 
decisions in due course. As regards the alteration in the nerve-structure 
itself, the characters it presents are very variable; at onetime it has been 
found wasted, at another hypertrophied and indurated, and so on. In¬ 
vestigations on the subject have left off where they should have begun, 
and we are consequently in great need of numerous properly prepared 
dissections at variable periods after the occurrence of the disease, to 
ascertain which portion of the tissue becomes first affected. The micro¬ 
scope will, doubtless, reveal alterations in structure which cannot be 
discovered by the scalpel; and in some future prosecution of the pathology 
of the disease it will lend its certain and valuable aid, which latter, I 
hope, may not be at a very distant period. 
Troceeding to our next head, “ Broken Wind,” speaking of the nature 
of this malady, I have to unhesitatingly assert that it is primarily and 
purely a nervous disorder, dependent on the condition of the digestive 
organs in which this pneumogastric nerve is also specially involved. It 
is produced by more than one cause; but the special one in this case 
undoubtedly is the continuance of ill-conditioned provender, and it is 
consequently a disease which, as a rule, takes some time to develop itself; 
but it does occasionally occur suddenly after severe exertion; when such 
is the case, it must, of course, originate in the lungs, causing, as we after¬ 
wards observe in our 'post-mortem examinations, an apparent rupture of 
air-cells. In its main cause, the pneumogastric nerve becomes slowly 
but gradually deprived of motory force in its digestive peripheries, and 
secondarily the respiratory portion sympathises, this being followed by a 
loss of respiratory power. To observe this peculiarity in its earlier stages, 
we must accustom ourselves to the normal appearance of respiration, 
