Page:Popular Science Monthly Volume 77.djvu/192

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URING the last ten years the sciences of bacteriology and parasitology have been established beyond previous expectation. To-day these sciences are so far-reaching that they not only have to do with medicine but extend into the realm of hygiene, agricultural sciences and the industrial arts. The advances made in connection with the life histories of the various microscopic animal parasites and the studies which have led to a general understanding of the relation between parasite and host have done much toward unearthing mysteries of diseases which attack domestic fowls and menace the poultry industry. Bacteriologists have enabled the avian pathologist to study and control these fatal diseases.

Practical applications of bacteriology to the arts and industries are only instances of the ramification of this science. In agriculture and closely allied science, bacteriology and also parasitology have been immediately and intelligently employed to set forth new facts and expose new problems. During the last few years bacteriology has held close relations with medical science. By the application and extension into the field of protozoon pathology one of the latest and most helpful developments in the study of infectious diseases has evolved. This is not alone true of human pathology, but must include avian, insect (such as bee and silkworm), sheep, swine and cattle diseases and possibly the diseases of plants.

In the poultry yards epidemics of the so-called "white diarrhoea," "black-head" of turkeys, and tape-worms, have demanded scientific study for remedial help. The loss to the poultryman is at present almost incalculable. The etiology of many diseases is understood only by the discovery of some bacteria or parasite. The mode of entrance of the invading microorganisms to the avian body, the study of the original source of the infectious material and the possibilities of transmission and infection can be apprehended only through prosecution of detailed bacteriological and parasitological studies. Individual birds may suffer from malnutrition and be afflicted with ailments which may be the result of inability to utilize food properly, but when a whole flock becomes droopy, listless and unable to maintain normal life, we must resort to the field of parasitology or bacteriology for the cause.