Some remarks, as already stated, were made on this subject in the “Medical Notes on China;” it may be added that many circumstances might be cited, tending to show that there is a close connection, not only between the causes of cholera and periodic fever, but also between it and endemic fever generally. All this is very vague and unsatisfactory, but with such generalities, negatives and probabilities, it is feared we must for the present at least, be as content as we can, unless we are disposed to leap to conclusions, without finding the steps of evidence by which alone they can be safely reached; or are willing to subscribe the creed, that cholera, however first produced, is reproduced only through the instrumentality of the human body—that, by whatever acts, combination of acts, or of accidents it began, it is continued solely by contagion. The essential cause of cholera—the _causa sine qua non est_—as well as of other things in nature with what are more familiar, is, and perhaps ever will be, beyond the reach of human penetration; and were its nature and properties ascertained, such knowledge might contribute little or nothing to our means of resisting its effects. But while this ignorance exists, and candour requires its confession, there is none respecting the associated concurrent agents, through whose influence it acquires extended prevalence and augmented fatal force. They have been already alluded to, and are so palpable as to be beyond question; and as they are on the surface, and susceptible of abatement or removal, it becomes us to deal with them promptly, vigorously, and perseveringly. They divide themselves into two classes, the first of which concern private citizens, both as individuals, and as forming families; the second are subjects for legislative enactments, and consequent executive interference, constructive and restrictive. Respecting the first, it may appear superfluous to reiterate what has been so often repeated, and universally admitted, namely the paramount importance of sobriety, cleanliness, and industry, in conjunction with sufficiency of nutritious food; nor to aver that if the former were more sedulously practised, there would be much less ground for complaint of the last than unhappily there is. It would be out of place to enlarge on such a subject here, but it may be allowable in passing to observe, that it behoves the more intelligent and wealthy members of the community, lay as well as clerical, to unite and help the more ignorant and needy in the great—vast as to results—reform, which it contemplates and embraces. A good deal has been attempted, and something has been done, but much is wanting. The work is great, requires many labourers, and gives scope for the combined exertions of enlightened philanthropists of all kinds. Yet we may say of it, without profanation or levity, and in the literal meaning of the words—truly the harvest is great but the labourers are few.