Wood and Coal Tar. impure Pyroligneous Acid. Petroleum. Smoke. Of these it is necessary to say little else than that they appear to have more or less of the preservative property in animal putrefaction; and that whatever power they possess is probably ascribable to the small quantity of carbolic acid which they contain. The extraordinary efficacy of tar ointment, as a local remedy in porrigo or favus, may be referred to this cause, partly, if not exclusively; the carbolic acid contained in it destroying the peculiar microscopic fungus of that disease. The free use of tar about ships no doubt contributes to their healthful-ness through a similar agency; while it serves to protect the timber to which it is freely applied, both here and elsewhere, against decay consequent upon the attacks of the lower forms of organic life. The same remarks are applicable to pitch, though in a less degree, and to coal-tar, probably even in a higher degree.

impure Pyroligneous Acid, which is the result of the distillation of wood in close vessels, contains, besides acetic acid, various empyreumatic products, among which is creasote and possibly other substances of the carbolic acid series. Hence, it is applicable to the same disinfectant and antiseptic purposes as tar, and is probably even more efficient for some purposes, in consequence of its greater fluidity. it was at one time considerably employed as a dressing for foul and gangrenous wounds and ulcers, and offensive suppurating surfaces, and as a gargle in malignant angina and scarlatina, and not without advantageous results. But it has in a great measure been superseded by creasote, or its aqueous solution.

Petroleum, which is probably a natural product of the distillation of vegetable matter, has properties analogous to those of tar; but, as it has not been extensively employed as a disinfectant or antizymotic, there is little to be said of it in this respect on the ground of experience; and I must content myself with referring to a somewhat elaborate article on the subject in the third part of the 12th edition of the U. S. Dispensatory.

Smoke, whether of wood or bituminous coal, has the same preservative power; and the former, as every one knows, has long been employed in the curing of meat. There can be little doubt that it owes this property to the same acids, resulting from the decomposition of the wood. in some parts of the world, cottages are purposely so constructed as in a considerable degree to retain the smoke generated in them. This is generally regarded as an evil; but it is probably of great service by destroying the morbific effluvia, often abundantly generated in such dwellings, crowded as they are, and kept close in winter to guard against the cold. in neighbourhoods rendered unwholesome by poisonous emanations from vegetable and animal decay, the slow burning of wood, so as to fill the air with smoke, will be advisable at certain seasons, should other more effective means not be available. it is an opinion entertained by some persons in miasmatic regions, that they can guard themselves against the fever by keeping fires in their houses during the latter part of summer and early autumn. The smoke may tend to destroy the malarial germs floating in the atmosphere. I have before referred to the application of burning sugar, to the sweetening of the air of the sick chamber, after the use of the close-stool. A little sugar is put upon some red-hot coals in a shovel, and thus carried around the apartment. it is not simply the agreeable and refreshing odour of the caramel, resulting from the combustion of the sugar, that is obtained in this case. The offensive odour is not only covered by that of the fumes, but, according to my observation, is absolutely destroyed; showing that there is some principle in the smoke of sugar, analogous to the carbolic acid which has been under consideration.