THE remarkable progress in sanitation which the last century has witnessed has been due largely to the progress of science. While it is customary to associate all reforms in sanitation with the medical profession, it cannot be denied that the ability which the medical profession has shown in sanitary matters has been largely due to the position which scientific studies hold in medical education. While all sciences have contributed more or less to this progress, there is one which stands out prominently as a controlling factor, namely, the science of chemistry. Intimately associated with this science, and as a part of it, must be reckoned bacteriology. The mere study of bacteria of all kinds in regard to their life relations has little to do with sanitation. is the bacterium as a chemical re-agent which the sanitary expert must deal with.

It

It is the purpose of this address to set forth briefly some of the points in which the science of chemistry touches the public health. Although the science of statistics is not as exact as that of many others, yet from the best evidence at hand, it is believed that the average of human life is considerably greater than it was a century or even a half-century ago. This increase in the length of life is certainly not due to any additional vitality in the organism, but results solely from the improvements in sanitation which the century has witnessed.

*Read before the Hundred Year Club, Dec. 11, 1902.

No. I.

These improvements may be grouped together as pure air, pure food, pure drugs, and greater immunity from contagious and enzymic diseases. In securing all these improvements chemistry has been an active factor In regard to pure air, chemistry has pointed out the sources of contamination, especially in the neighborhood of large cities, to which the air is subject, and devised means for their suppression. Especially in large manufacturing and metallurgical centers, where immense volumes of noxious gases are poured into the air, unless special precautions are taken, grave injury to public health may result. Chemistry has shown how these gases can be almost completely oxidized, since in many cases more perfect oxidation produces a more harmless product. For instance, it might be cited that when carbon is burned with an insufficient supply of oxygen one of the products of combustion is carbon monoxide, a gas which is far more injurious to health than the complete product of combustion, namely, CO,. On the other hand, it is known that some of the higher forms are more noxious than the lower forms, as, for instance, sulfuric and nitric acids. In these cases science has pointed to the way of condensing and recovering these bodies for economical purposes, and thus freeing the air from their presence. If the products of combustion are noxious and useless for technical purposes science has pointed to the