On the mode of communication of cholera / by John Snow.

  • John Snow
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: On the mode of communication of cholera / by John Snow. Source: Wellcome Collection.

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    been employed on the opposite side, and that many eminent men hold an opposite opinion; but, besides the objection that negative evidence ought not to over¬ throw that of a positive kind, the instances that are believed to oppose the proofs of communication are reasoned upon in the opinion that cholera, if conveyed by human intercourse, must be contagious in the same way that the eruptive fevers are considered to be, viz., by emanations from the sick person into the surrounding air, which enter the system of others by being inhaled, and absorbed by the blood passing through the lungs. There is, however, no reason to conclude, d priori, that this must be the mode of communication of cholera; and it must be confessed that it is difficult to imagine that there can be such a difference in the predisposition to be affected or not by an inhaled poison, as would enable a great number to breathe it without injury in a pretty concentrated form (the im¬ munity not having been earned by a previous attack, as in the case of measles, &c.), whilst others should be killed by it when millions of times diluted. The diffi¬ culties that beset this view are of the same kind, but not so great, as those which surround the hypothesis of a cholera poison generally diffused in the air, and not emanating from the sick. Reasoning by analogy from what is known of other diseases, we ought not to conclude that cholera is pro¬ pagated by an effluvium. In all known diseases in which the blood is poisoned in the first instance, gene-
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