186 THE POPULAR SCIENCE MONTHLY 
BACTERIOLOGY AND PARASITOLOGY IN RELATION TO 
AVIAN DISEASES 
By GHO. EDWARD GAGE, Pxu.D. 
MARYLAND AGRICULTURAL EXPERIMENT STATION 
URING the last ten years the sciences of bacteriology and para- 
sitology 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 sci- 
ences 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 in- 
dustry. 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 diarrhea,” 
“lack-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 en- 
trance 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 prosecu- 
tion 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. 
