Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . Fig. 155.—Bacillus typhosus at beginning of Widal test. {Da Costa.) and is practically specific for any given organism. Widal, ^ in the same year,applied this principle to the diagnosis of typhoid fever, showing that clumpingand loss of motility of the typhoid bacilli occur when a suspension of the activelymotile types is treated with an homologous immune serum at such a dilutionthat normal or non-homologous serum does not react. I. Gruber-Widal Fig. 156.—A pseudo-Widal reaction
Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . Fig. 155.—Bacillus typhosus at beginning of Widal test. {Da Costa.) and is practically specific for any given organism. Widal, ^ in the same year,applied this principle to the diagnosis of typhoid fever, showing that clumpingand loss of motility of the typhoid bacilli occur when a suspension of the activelymotile types is treated with an homologous immune serum at such a dilutionthat normal or non-homologous serum does not react. I. Gruber-Widal Fig. 156.—A pseudo-Widal reaction. {Da Costa.) Cultures. The cultures of the typhoid bacillus must be fresh and must show many actively motile organisms in the hanging-drop specimens, if they are to be used in the microscopic method. It is advisable always to use cultures containing about the same number of bacilli, as the reaction is somewhat quantitative. » Bull med. Paris, 1896, X, 618 and 766. 6o8 DIAGNOSTIC METHODS. Thus, if few bacilli be present, they may be clumped by a small amount ofagglutinin both specific and non-specific, while if the number be very large, thespecific agglutinin may not be sufl&cient to cause marked clumping and lossof motility of the organisms. Great differences toward agglutination exist indifferent strains of the typhoid bacillus, so that it is essential always to employ,for diagnostic purposes, strains which have passed through several generationson artificial media. A stock culture of the bacillus is kept in sealed tubes of nutrient agar in ac
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