Medical Officers of the Army of India.
53
The practical bearmg which a theory of this kind has on the question of
the means which ought to he adopted in any endeavour to protect a locality
from invasion by epidemic cholera is evident. So long as it is, assumed that
the specific cause of the disease finds its proper site for manufacture and multi-
plication within the human body, it is conceivable that, were it possible anywhere
to carry out theoretically perfect quarantine measures, the exclusion of the
disease might be secured although at a disastrous cost, but if its development
take place in the environment, the only efficient quarantine measures would lie
in permanent cessation of all communication with any locality in which the
disease had ever manifested itself. The experience of every epidemic in Europe
shows that the agents concerned in the elaboration of the specific poison may
lie dormant for periods of many months, and then again manifest their presence
when the local conditions once more become favourable to them, so that the
mere absence of cholera from a locality affords no security of the absence of
the factors of the choleraic poison. The presence of the disease shows that
factors are in activity, its absence does not show that they are absent, and
hence any locality in which cholera has ever localised itself becomes a possible
site from which they may be imported, and this of course implies that in order
to avoid importation securely all intercourse with it must be permanently aban-
doned. But even a permanent cessation of traffic would not be certainly pro-
tective, as human traffic is not the only means whereby materials are conveyed
from one locality to another. If birds are an efficient means in aiding the diffu-
sion of seeds and molluscs from one site to another, they most assuredly may
well be capable of conveying organisms of the nature of those presumably giving
rise to the development of the choleraic poison. Efficient prevention of the
importation of the factors of the choleraic poison according to this view
becomes as theoretically impossible, as the attempts to secure it are undoubted-
ly ruinously expensive and futile, but this does not imply that it assumes that
nothing can be done to prevent the invasion of localities by epidemics. On the
contrary, whilst it puts an end to all hope of effectively excluding the introduc-
tion of the factors, it holds out a possibility of rendering such introduction a
matter of no importance. Had the site proper to the existence and activity of
the factors of the poison been the human organism, we should, in the failure of
quarantine, been left without hope of being able to influence the diffusion and
prevalence of the disease, but this is not so when we accept the environment as
the site, and assume that the presence of certain conditions in it are necessary in
order to allow the factors to exercise their activity. In the absence of know-
ledge of the precise nature of the factors, we are unable precisely to define what
these conditions are; but, what we do know is, that all general sanitary improve-
ments do affect the liability to prevalence of the disease, either by preventing
the manufacture of the poison or preventing its access to the human organism
subsequent to manufacture. Any quarantine measures which could ever be