. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. COCCACE^ AND THEIR~PARASITIC RELATIONSHIPS 267 positive. In cultures the capsules are less well developed and often cannot be demonstrated at all. The individuals are often less pointed and frequently resemble short bacilli in form. They may remain attached together in chains of six to eight cells. Cultures may be obtained on ordinary media but they are prone to die out quickly. Blood-agar, serum agar or ascitic-fluid agar ar
. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. COCCACE^ AND THEIR~PARASITIC RELATIONSHIPS 267 positive. In cultures the capsules are less well developed and often cannot be demonstrated at all. The individuals are often less pointed and frequently resemble short bacilli in form. They may remain attached together in chains of six to eight cells. Cultures may be obtained on ordinary media but they are prone to die out quickly. Blood-agar, serum agar or ascitic-fluid agar are the best solid media, but even with these weekly trans- plantation is usually necessary. Broth to which serum or ascitic fluid has been added forms an excellent medium. There is prac-. FiG. —Pneumococcus, shoTidng capsule, from pleuritic fluid of infected rabbit, stained by second method of Hiss. 'tically no growth below 25° C. On blood agar, the colony is surrounded by a zone of greenish discoloration, a character of great value in the early recognition of the pneumococcus isolated from the body. The virulence of the microbe diminishes very rapidly in artificial culture. Virulent material is best kept in stock by preserving in a desiccator dried blood taken from a rabbit dead of pneumococcus infection. The fluid blood may also be kept in sealed capillaries in the refrigerator. By these methods the virulence may be preserved for months. Rabbits, mice and , young ral^s are the most susceptible Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original MacNeal, Ward J. , 1881-1946; Williams, Herbert Upham, 1866-. Philadelphia, P. Blakiston's Son & Co.
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