About thirty years ago, as I have already remarked, one of the most distinguished practical geologists of this or any other country directed his attention to a subject of much greater difficulty than the classification of rocks, and their subdivision into primary, secondary, volcanic, and transition. His object was to discover the origin or cause of those fatal diseases which, under the names of fever, dysentery, plague, rheumatism, &c., render the position of man on the globe so precarious, his life at times so brief, valueless to himself or to others, his prospects so gloomy; in brief, by tracing to its origin, if possible, the active agent of such woes to man, to destroy its fatal influence by practical hygienic measures. In a word, Dr. Macculloch hoped, by discovering the cause, to devise the means either of effectually destroying malaria--using the term, however, in a sense at that time peculiar to himself--or so to mitigate its effects as to render it less destructive to mankind.
He, an acute and original observer, statistician, and scientific man, properly so called, did not require to be instructed as to the lamentable results which the premature death of millions causes to the surviving relatives--results so eloquently and so correctly depicted by the illustrious Quetelet in his work on Man.[4] Of all this he was well aware, and a consciousness of such a condition of humanity, and a firm belief in the opinion that the cause lay in some defect in our social system, remediable by human means, led to those inquiries on which the late Dr. Macculloch based his theory of a universal malaria the cause of most diseases--a theory now adopted in its entirety by a large section of the medical faculty, and by the English Government of the present date.
The theory or theories of Macculloch,[5] as expounded by himself, amounted in fact to this--that a poison, which may be called malaria, is generated by vegetable and animal substances whilst undergoing decomposition or putrefaction, and that to the presence of this poison may be traced most of the diseases afflicting civilized man. In a neglected drain or sewer he saw the cause of typhus, of agues, of skin disease, neuralgias, &c.