at the beginning of the present century. It was freely employed in hospitals, both civil and military, in prisons, workhouses, etc., and was supposed to be efficacious against fevers, cholera, and small-pox. Whenever its characteristic odor could be perceived, danger of infection was no longer feared. Persons carried about with them small flasks containing chemicals which generated this gas, and inhaled a little when they considered themselves exposed to risk. It soon, however, became evident that these precautions were useless; but even so recently as 1866, during the war between Austria and Prussia, it was thought sufficient to distribute saucers containing chloride of lime throughout the military hospitals, while only feeble efforts were made to insure cleanliness and other important sanitary requirements. In order to act as a real disinfectant, chlorine must be employed in a very different manner. The terrible mortality after surgical operations and severe injuries, a feature of which was that a large majority of patients died with symptoms of blood-poisoning, showed the futility of such attempts at disinfection.
In spite, however, of many similar failures, deodorization has been almost universally regarded as the main object to be accomplished, and other chemical agents have been used in order to combat the gaseous products of decomposition. This object could certainly be attained if the sense of smell were to be the sole judge of success, and the practice of deodorization led also to the discovery and use of many substances which have the power to prevent or retard putrefaction, and were therefore termed antiseptics, and regarded as equivalent to disinfectants. The conclusion, however, was soon forced upon the minds of experimenters that the infective agencies of fevers, small-pox, etc., were neither offensive gases nor the products of putrefaction, but something of an entirely different character. When an infectious disease became associated with the idea of a transportable material which increases and multiplies in its new ground, the discovery was not far off that organisms capable of reproduction are the real causes of the disease.
Definite ideas now prevail as to what is meant by disinfection, and as to the methods by which this object can be attained and the tests whereby their efficacy may be proved. Any substance may be regarded as a true disinfectant which, when added to a quantity of fluid swarming with bacteria, abolishes the reproductive power of these organisms. If the bacteria are capable of producing disease, or the poison of disease, a successful experiment has been made in the way of disinfection. This fact explains the paucity of the real experiences we possess of disinfection proper. Heat, exposure to air and sunlight, and the use of chemical agencies are the means at our disposal; it will be sufficient to point out a few of the methods in which they may be employed.
A very high temperature will, of course, destroy all forms of organized matter, and if we could always isolate the germs of disease and
