Note 37 — SECOND ANNUAL REPORT.

For the professional reader I may here throw out a hint—referring to the doctrine of epidemic disease stated in the Fifth Annual Report, that this apparent healthiness of districts after certain epidemic invasions probably bears relation to a temporary exhaustion of their zymotic atmosphere under the action of a specific ferment, and is in some respects analogous to that immunity from an infected fever which belongs to an individual who has recently suffered its attack. See also page 235.—J. S., 1854.