Page:Popular Science Monthly Volume 48.djvu/820

738 moistened with, a culture of a bacillus which causes a fatal infectious disease among these little animals.

In Greece, in Hungary, and in other parts of Europe the quantity of grain consumed by field mice constitutes a very serious loss. Recent experiments made with cultures of two different bacilli (Bacillus typhi murium of Löffler and the bacillus of Lasar) show that it is practicable to destroy these pests, in the fields where their depredations are committed, in the manner indicated. Mice which consume the bread moistened with cultures of one of the pathogenic bacilli referred to die within a short time from general infection, and their bodies are consumed by other mice, which also become infected. Thus a veritable epidemic is induced by which their numbers are very materially reduced.

This leads us to the subject of the prevention of infectious diseases among domestic animals. We have now a precise knowledge of the specific infectious agents ("germs") in the diseases of this class which have caused the greatest losses. The most important of these are anthrax, glanders, tuberculosis, infectious pleuro-pneumonia, swine plague, hog cholera, hog erysipelas, and fowl cholera. All of these have been proved to be due to bacterial parasites, the morphological and biological characters of which are now well known. The infectious agent and usual mode of infection being known in any given disease, we have a scientific basis for measures of prophylaxis. These naturally include the destruction of the specific micro-organism to which the disease is due wherever it may be found. An enormous amount of experimental work has been done for the purpose of determining the comparative value of disinfecting agents and the practical advantages of each, having in view questions relating to cost, stability, solubility, odor, toxic properties, etc., also to the difference in resisting power of different pathogenic bacteria, the presence or absence of spores, the character of the material with which they are associated, etc. As a result of this extensive laboratory work our knowledge with reference to the efficiency and availability of agents of this class is very complete, and enables those who are familiar with the experimental evidence to formulate rules for the destruction of the various pathogenic bacteria wherever they may be found. The infected animal is itself a focus of infection which under certain circumstances had better be destroyed in toto, the individual being sacrificed and the body put out of the way of doing harm by means of cremation or burial. Under other circumstances it may be sufficient to isolate the infected animal and to disinfect all discharges containing the pathogenic germ and all objects contaminated by such discharges. By such measures the extension of epidemic diseases fatal to