690 ON MURRAIN, OR THE VESICULAR EPIZOOTIC. 
also be adduced as proving that the disease is able to communicate 
itself to animals previously in a sound and healthy condition. 
Not only is the disease capable of communicating itself by con- 
tact or proximity, but the specific poison is actively diffusible ; it 
spreads to considerable distances without becoming innocuous by 
dilution, and is retained by fomites (substances capable of absorbing 
and retaining contagious effluvia) for a long time without its viru- 
lence being abated. In proof of this, it might be stated that cattle 
have contracted the disease from being driven along a road over 
which diseased animals had passed some time before ; and also 
that, in all probability, contagion can be transmitted to healthy 
stock by the clothes of herdsmen and others being impregnated 
with the virus evolved from the bodies of animals affected by the 
disease. Distinct evidence has also been brought forward that the 
subtile pollen-like principles of the disease have been wafted over 
considerable spaces, and have sown themselves in some new spot 
previously un visited by the malady. 
The time that intervenes between exposure to the influence of 
contagion, and the first appearance of the disease, varies much in 
different cases, and is doubtless modified by the intensity of the 
specific poison, and the idiosyncrasy of the individual. The symp- 
toms have sometimes appeared within three days, and sometimes 
not for a week, after the application of the exciting cause. 
Cases are recorded in which animals, contrary to the general 
rule, have had the disease more than once. Such cases, are how- 
ever, of so infrequent occurrence, that we may safely assume, that 
the fact of an animal’s having been affected once, protects it ever 
after from a second attack. This being an ascertained truth, we 
are naturally led to consider the advantages and disadvantages of 
inoculation. As long as there is the slightest chance of their es- 
caping the disease, it would evidently be the greatest folly to in- 
oculate animals unaffected by it. But when the malady has appeared 
among a stock, and when we apprehend that it will in all pro- 
bability affect animals having even the most distant communication 
with the sick ones, it then becomes a question whether it may not 
be advisable to inoculate the whole of the intact stock with matter 
taken from a 7nild case. The malady thus excited has been as- 
certained to be less severe than that produced in the natural way, 
the symptoms being usually less aggravated and the duration 
shorter. Such being the case, it is probable that in districts where 
the disease is of a malignant type, inoculation might with ad- 
vantage be tried among that part of the stock as yet unaffected. 
Even although the animals have been previously affected in the 
usual way, the inoculated or milder form of the disease gets the 
start of the severer and more complicated type, and, running its 
