516 
Pleuropneumonia amongst Cattle. 
By George Waters, Jun . , M.R.C.V.S., Corn Exchange Hill , 
Cambridge. 
PRIZE ESSAY. 
Mode of Infection. 
[Continued from page 416.] 
Before stating my opinion on the “Mode of Infection,” I shall 
take the liberty of bringing forward a few general considerations 
on the circumstances which appear to exercise an influence on 
the original production of a disorder, which, infectious though it 
may be, comes nevertheless within that class of diseases termed 
Epizootic. 
The subject of epizootic diseases is one of an extensive range, 
and admits of a wide field for speculation ; there are, however, 
some general as well as particular circumstances which we should 
not be justified in overlooking. The manner in which this, or 
diseases of a similar kind, are not only observed to prevail over 
extensive districts of the same country, but also in different 
countries themselves, would lead us to ascribe their origin, as well 
as their specific character, to peculiar atmospheric conditions ; but 
as yet so little has been positively ascertained regarding those 
conditions, that, whilst we are obliged to take them into account 
in dealing with the general history of the disease, we are not 
able to draw any practical application from them. I may, how- 
ever, mention that unusual and irregular weather — the prevalence 
of particular winds — varieties of season, as drought and moisture — 
may exercise some influence on the development of the disease : 
but what is of more practical importance, that local conditions, 
either as regards situation of pasturage and quality of herbage, 
impurities of stabling, stall-food, either defective in quantity or 
quality, may also materially contribute to its production. 
And in addition to the abovementioned external causes, I must 
not fail to call attention to those conditions in which foreign cattle 
are placed before they arrive in this country — such as a voyage 
by sea, confinement on deck, &c. ; or the manner in which they 
or home-bred cattle are driven from one place to another, under 
which circumstances they are made to undergo much fatigue, and 
are generally obliged to pick up food by the roadside, or in limited 
pastures, being at the same time exposed to all varieties of the 
weather. However, many of the inconveniences connected with 
