“Here we find that, though in the last of these years the maximum height of water in the lake happened to correspond with the greatest prevalence of fever, the latter can by no means be looked upon as a consequence of, or in any way connected with, the former; since in 1818, when the water rose to within a few inches of the same level, there was less fever than in any of the years under observation; whereas in 1820 and 1821, when the waters of the lake appear to have been at the minimum, there was more than in any of the years prior to 1828. “This supposition seems to have originated in the circumstance of fevers being generally most prevalent from June to October, which happens to correspond with the period when the waters of the lake are at the greatest height; but the wide sphere over which these statistical investigations now extend, has enabled us to show that febrile diseases always prevail most at that season of the year, even in countries where no such cause is in operation to produce them; consequently, the rise of the waters in the lakes can no more be regarded as the cause of fever in America, than the cessation of the trade winds about the same period can be deemed a satisfactory reason for the appearance of that disease in the West Indies. Both are merely coincidences which, by those who have not a sufficiently extensive field of observation, are apt to be mistaken for causes.” There arises out of all such inquiries one obvious deduction--viz., that the essential nature of malaria is altogether unknown; and that unless we choose to remain contented with such vague hypotheses as those of Macculloch, now adopted by the Medical Board of Health of Great Britain,[25] other inquiries must be entered on. The assertion is as easily made as its refutation is difficult, that typhus fever is caused by a neglected drain or ditch; that scarlet fever, small-pox, and cholera have for their origin the same cause; that if they do not immediately produce the poison, they predispose the human frame for its reception; and that as a necessary result, all such diseases, and deaths resulting therefrom, and from zymotic forms of disease generally, are preventible by human agency. Let us leave these Utopian views to the clever pens skilled in the art of making that seem new which is not new, and that seem true which is not true, and patiently inquire into some of the many difficulties besetting all investigations into Nature’s processes, and man’s interpretation of them.[26] [25] As by the Registrar-General: see his Reports. [26] The ancient Egyptians seem to me to have long ago settled this question, practically. On the subsidence of the Nile they, without a day’s delay, commenced agricultural operations; nothing was allowed to fall into rottenness or putrefaction. CHAPTER VI. THE LIVING WORLD--ITS EXTENT AS REVEALED BY THE MICROSCOPE--HOW ITS REMAINS ARE DISPOSED OF WHEN LIFE HAS CEASED.