Page:Popular Science Monthly Volume 77.djvu/194

188 body of the bird aud consequently eliminate infection. Contributions from the Division of Biology of the Rhode Island Experiment Station have furnished us interesting facts concerning parasitism of Cytodites nudus, a mite and Hæmaphysalis chordeilis, a tick and these are but a beginning to the study of such parasites affecting birds. It demonstrates the field for research in parasitology and what contributions from this realm of science would mean in determining the cause of so many diseases, the etiology of which at the present time is unknown.

Fowl typhoid, cholera, tuberculosis and hosts of other afflictions were discovered through the aid of scientific bacteriologists. In a very recent publication Professor Rettger, of Yale University, has demonstrated the value of bacteriology, by his valuable contribution to the study of white diarrhœa. He has been able to demonstrate the rôle of bacteria in the etiology of this disease. We need no better example of the usefulness of such a science in planning investigations of this nature. By thorough bacteriological methods he has been able to give us the results of his work and has shown how infection may occur, what it means to the poultry industry, and methods of prevention. This also demonstrates how bacteriological methods have been used to study epidemiology. It has given a procedure based on bacteriological facts and with such methods at hand we are supplied with the means of suggesting treatments which undoubtedly will do much toward solving the problems which have heretofore been unsolved. These studies have shown that the function of pure water and food and sanitary conditions are essential to the daily life of domestic birds. If diseases of the poultry yards are to be suppressed, hygienic measures must be observed here as with human beings. It was not until after the introduction of hygienic measures such as a proper sewage disposal, and water filtration that the death rate of typhoid fever was perceptibly diminished in this country and Europe.

Conspicuous as the achievements have been in bacteriology, it can not be said that the field is exhausted. There is hardly an infectious disease of the poultry yards which does not have to do with some bacterium or parasite, and the variations and adaptations of these pathogenic forms is to-day one of the difficult problems with which the avian pathologist has to deal. It is for the scientist to determine whether certain bacteria and parasites owe their pathogenic action to the organisms themselves or to their toxic or poisonous by-products. The field of immunity as related to avian pathology is unexplored. This would be among the most complicated that the scientist could undertake, yet the fields of bacteriology and parasitology with its many perfected methods of attack would indicate that it is not impossible. Not only human medicine, but also veterinary science owe much of their