As the subject appears one which may interest the general reader, it is proposed to add a few observations on the diseases which are caused by air vitiated with effluvia from the soil. CHAPTER VII. MALIGNANT FEVER. A vast proportion of the most virulent diseases to which the human race is subject in almost all parts of the world, but more especially in tropical regions, is produced by the action of effluvia arising from decomposing dead animal and vegetable matter on the surface of the earth, and incorporated with the soil. These effluvia are the immediate instrument by which thousands of our fellow men are annually deprived of existence, the career of the young and the robust is abruptly stopped, never again to be renewed. Malignant fever is the disease, by which death is occasioned from these effluvia; and this fever assumes forms, characters, and titles, various and manifold. It ravages in almost every country within the tropics, and in many situations it annually commits the most dreadful havoc—cutting down so rapidly that the ordinary forms of burial cannot be observed. Whole communities suffer, the inhabitants of a particular tract of country are sometimes almost extirpated, and to visit some countries is almost to incur death from pestilence, so near to certain is attack, and its destructive character is so uniform. The average duration of life in many countries is extremely low, chiefly on account of the wasteful career of that scourge, under its various characters and designations; and it is not saying too much that there the number of deaths is four times as great as occurs in our own happy country. In those regions in which malignant fever prevails so much, almost every inhabitant at one period of his life, sooner or later, is afflicted with it. If he survive he is more fortunate than thousands of those who lived beside him; but his health is often deteriorated, he is often deprived of that vigour and elasticity both of mind and body, which spring from a sound constitution, and he not unfrequently lingers under the sufferings of chronic disease till his life is gradually though slowly exhausted; unless, indeed, as often happens, it is suddenly terminated by a fresh attack of the active pestilence.