AVIAN DISEASES 187 
In the warfare against the ravages of disease a most rational 
hygiene of the poultry yards must be observed, and in order to under- 
stand thoroughly those factors which have to do primarily with elim- 
inating the trouble, it is to the use of disinfectants and antiseptics that 
we must resort. Here again the science of bacteriology lends a helping 
hand, for data concerning the efficiency of disinfectants can be ascer- 
tained only by bacteriological technique. It then becomes the duty: of 
the scientist to direct his entire attention to those factors which in 
themselves are sufficient to allow a foothold for many an infectious 
disease. It is no less a fact among domestic birds than with human 
beings, that infection may take place by contaminated food, the par- 
ticular parasite or organism being transmitted in such manner. All 
the modes of spread are recognized, and just as the spread of human 
diseases are held to be matters of public concern and preventive measures 
are instituted by expert bacteriologists, so also should the spread of 
diseases among domestic fowls be of the same great concern to the 
poultryman if he is desirous of maintaining his birds in a healthy 
condition. 
Probably one of the most difficult problems in relation to avian 
diseases lies in the prompt recognition of the cause, so that measures 
may be employed immediately to allay the trouble. With the large 
poultry farms it may appear that careful observation of hygienic meas- 
ures involve too much time, but under many circumstances and espe- 
cially at this infant stage in our knowledge concerning avian diseases 
the application of searching and delicate parasitological and bac- 
teriological tests are often necessary to determine the proper method 
of procedure. 
The great losses to poultrymen from the disease known as “ black 
head ” or “ coccidiosis of turkeys” has called scientific men to make 
thorough investigation and a specific parasite known as a coccidium 
has been claimed to be the cause. Dr. Geo. B. Morse, of the Bureau of 
Animal Industry, United States Department of Agriculture,’ states that 
this coccidium may infect turkeys, ducks and pigeons. It has a defi- 
nite life cycle. He describes it as a certain circular, sometimes slightly 
oval, cyst, 12 to 25 microns in diameter, containing granular matter 
which may fill the cyst or occupy only a portion of it. These are per- 
manent cysts and may be voided in the feces of the bird. These only 
require warmth and moisture for their development into sporozoites by 
which the disease is transmitted to other birds. By the destruction of 
the malarial parasite within the body of man, we may break the life 
eycle and thus interrupt the continuity of the transfer between man and 
mosquito in the transmission of this disease. In like manner, the 
scientist can plan to break the cycle of these avian parasites within the 
*Cireular 128 (1908), Bureau of Animal Industry, Dept. of Agriculture. 
