7
ment of cholera within their bounds, is a fact which does not preclude transmissibility ;
but which indicates that certain places, not yet all determined, are an obstacle to the deve-
lopment of the disease. The more or less complete and the more or less durable immunity
which the greater number of persons placed in a choleraic centre enjoy, an immunity
that attests the individual's resistance to the poison, is a circumstance which should be
held to be of the greatest value. Viewing it with reference to epidemic development,
it is corrective of the transmissibility, and, as regards prevention, it puts on the way,
means fitted to restrain the ravages of the disease.
" Question 28th.—From the facts previously established, and which are con-
nected with the generation, the propagation and the transmissibility of Cholera, can
we deduce any thing precise as to the generating principle of the disease, or, at least,
as to the mediums which serve as vehicles, or receptacles ; as to the conditions of its
entrance into the organism ; as to the ways by which it escapes from it ; as to the du-
ration of its morbific activity ; in short, as to all the properties, a knowledge of which
concern prophylaxis ?
" Answer.—In the present state of science we can announce only hypotheses
as to the nature of the generating principle of Cholera ; we know only that it is indige-
nous in certain countries of India, and that it maintains itself there permanently ; the
principle reproduces itself within man, and accompanies him in his peregrinations ; it
may thus be diffused to a distance from country to country, by its successive re-produc-
tion, without ever generating itself spontaneously, apart from man.
"Question 29th.—What are the vehicles of the generating principle of Cholera?
" Question 30th.—To what distance from a centre of emission can the principle
of Cholera be carried by the air ?
" Answer to 29 and 30.—The ambient air is the chief vehicle of the generating
agent of Cholera ; but the transmission of the disease by the atmosphere, in an immense
majority of cases, is limited to a distance very close to the centre of emission. The in-
stances cited of transport by the atmosphere, to one or many miles distance, are not
sufficiently conclusive.
" Question 31st.—"What are the other vehicles of the choleraic principle ?
" Answer,—"Water and certain ingesta may serve as vehicles for the introduc-
tion of the generating principle of Cholera into the organism ; the ways by which the
poisonous agent penetrates are chiefly the respiratory, and very probably also, the
alimentary, passages. Nothing has been ascertained as to entrance by the skin.
" Question 32nd.—What are the chief receptacles of the choleraic principle ?
"Answer.— Choleraic dejections being incontestably the chief receptacle of the
morbific agent, it follows that all that is contaminated with those dejections also
becomes a receptacle, whence the generating principle of Cholera may be set free under
favoring circumstances. It follows also that the generation of the choleraic germ most
probably takes place in the alimentary canal, to the exclusion, perhaps, of any other
part of the organism.
" Question 33rd.—What is the duration of the morbific activity of the gene-
rating principle of Cholera ?
" Answer.—Observation shows that the duration of choleraic Diarrhoea, called
premonitory (which it is necessary not to confound with Diarrhoea that exists in times