. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . t only very serious, but they readily spread theinfection. The bacillus exciting the disease was discovered simulta-neously by Kitasato and Yersin (1894) during an epidemic of the bubonicplague in China. It is found in large numbers in the seropurulent fluid from the recent buboes charac-teristic of this disease and inthe lymphatic glands; morerarely in the internal organsexcept in pneumonic caseswhen the lungs and sputumcontain immense numbers. Itoccurs in the blood in acutehemorrhagic cases and s
. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . t only very serious, but they readily spread theinfection. The bacillus exciting the disease was discovered simulta-neously by Kitasato and Yersin (1894) during an epidemic of the bubonicplague in China. It is found in large numbers in the seropurulent fluid from the recent buboes charac-teristic of this disease and inthe lymphatic glands; morerarely in the internal organsexcept in pneumonic caseswhen the lungs and sputumcontain immense numbers. Itoccurs in the blood in acutehemorrhagic cases and shortlybefore death. It also occurs inmalignant cases in the feces ofmen and animals. The bacillus,as we have stated, is closelyallied to the hemorrhagic septi-cemia group. Morphology.—The bacilli insmears from acute abscesses orinfected tissues are, as a rule,short, thick rods with roundedends. The central portion of the bacillus is slightly convex. Thebacilli are mostly single or in pairs. Bacilli in short chains occur attimes. The length of the bacilli varies, but on the average is about. Fig. 148.—Involution forms on salt agar.(KoUe and Wassermann.) BACILLUS OF BUBONIC PLAGUS 423 ;tt ( to ), breadth * to Besides the usual oval form,the plague bacillus has many exceptional variations which are charac-teristic of it. In smears, especially from old buboes, one looks for longbacilli with clubbed ends (similar to involution forms (Fig. 148), yeast-like forms, and bladder shapes. Some of these stain with difficulty. Staining.—^They stain readily with the ordinary aniline dyes, andespecially well with methylene blue, the ends being usually more deeplycolored than the central portion; they do not stain by Grams method. Biology.—^An aerobic, non-motile bacillus. Grows best at 30° to35° C. Does not form spores. Grows on the usual culture media,which should have a slightly alkaline reaction. Does not liquefy well on blood-serum media. It
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