44
Scientific Memoirs by
whether in any individual instance we are dealing with a case which should or
should not be regarded as of truly choleraic nature. It has been hastily
assumed that an essential difference must exist between cases of true cholera
and cases of cholera nostras and of ptomaine poisoning because in the case of
cholera we are dealing with a series of symptoms which occasionally present
themselves in widespread epidemic fashion, and that the only explanation of
epidemic diffusion is to be found in a local multiplication and manufacture of
the essential toxic agents within the organisms of those who are affected by
them ; in other words, it has been assumed that true cholera differs from cholera
nostras or ptomaine poisoning, in that in true cholera we are dealing with
disease dependent on factors which are developed within the organisms of the
sick, whilst in the other case we are dealing with disease dependent on factors
of extrinsic origin which have been developed in the environment. But any
such assumption is entirely unwarranted by the data which are actually at our
disposal. The mere fact that certain morbid symptoms sometimes manifest
themselves in sporadic and at others in widely diffused epidemic fashion is no
evidence that in the two cases they are due to distinct causes, or to the
manufacture of one and the same cause in distinct sites, for,, if the cause in
both cases alike be one, which is normally developed in the environment, the
number of individuals on which it will act must necessarily be regulated by the
extent to which it is locally produced. Where only limited quantities are
developed and those only in isolated localities, sporadic cases of disease will
manifest themselves, where larger quantities are produced, but the process of
manufacture remains confined to isolated localities; local epidemics will arise,
and where it is produced in large amount and over wide areas, epidemic diffusion
will naturally take place. It remains thus not improbable that there is no
essential difference between epidemic cholera and cases of " cholera ,nostras "
or ptomaine poisoning, and that the apparent difference which presents itself is
simply the result of the absence or presence of local conditions favourable to,
or repressive of, the manufacture of one common cause. In local conditions,
however, it must be borne in mind that we may have to deal with two distinct
classes of factors whose co-operation is necessary to secure the development of
such a cause—factors which actually elaborate the specific cause of the disease,
and factors which favour or repress the process of manufacture. The absence
of the actual immediate cause of disease may thus not necessarily imply the
absence of permanent local conditions favourable to its evolution, but merely
an absence of the factors which under favourable circumstances are capable
of effecting the process of manufacture. In any locality, such as Calcutta, the
phenomena indicate the persistently coincident presence of both factors, in locali-
ties which are outside the endemic area the alternation of periods of exemption
with periods of epidemic prevalence might conceivably be due either to alter-
nating absence and presence of favourable local conditions, or to alternating
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