. The pathology and differential diagnosis of infectious diseases of animals. Veterinary medicine -- Diagnosis; Communicable diseases in animals. i8o TUBERCULOSIS slaughter houses of Kansas Cit}^ Omaha, Sioux City and Chicago are practically free from this disease. Tuberculosis exists, however, in many places where beef cattle are raised, as the result of the introduction of affected breeding stock. In many localities, especially where there is an extensive inter- change of animals, a large percentage of the herds are more or less affected. § 141. Etiology. Tuberculosis is caused by a rod-shap
. The pathology and differential diagnosis of infectious diseases of animals. Veterinary medicine -- Diagnosis; Communicable diseases in animals. i8o TUBERCULOSIS slaughter houses of Kansas Cit}^ Omaha, Sioux City and Chicago are practically free from this disease. Tuberculosis exists, however, in many places where beef cattle are raised, as the result of the introduction of affected breeding stock. In many localities, especially where there is an extensive inter- change of animals, a large percentage of the herds are more or less affected. § 141. Etiology. Tuberculosis is caused by a rod-shaped organism known as Bacterium tuberculosis. It was discovered by Robert Koch in 1882. Schiil- ler and Toussaint had previously studied growths which seem, from the results of their inoculation ex- periments, to have been this organ- ism. The bacterium of tuberculosis is a slender, rod-shaped organism with rounded ends, from 2 to 5/< in length and from to ; broad. The rods are straight or slightly curved, and occur singly, in pairs or in small bundles. Frequently they cross one another. They do not produce spores, but vacuoles are often observed and branching forms have been described. The bacterium of tuberculosis is readily cultivated on artificial media such as blood serum, glycerinated agar and bouillon after it has been adapted to such artificial conditions.* It is, however, not easy to cultivate it directly from ordinary. Fig. 30. Bacterium tuber- culosis. *To accomplish this necessitates a very special and careful proce- dure. Dr. Theobald Smith, of Harvard University (Jour of Exp. Med., Vol. III., 1898, p. 451), has the credit of formulating a method by com- bining details in such a manner that the procuring of cultures is, in most cases, possible. Dog serum is used. The method, as he gives it, is as follows : " The dog was bled under chloroform and the blood drawn from a femoral artery, under aseptic conditions, through sterile tubes directly into s
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