DIPHTHERIA 289 



slender rod, straight or slightly curved, and remarkable for its 

 beaded appearance ; there are also irregular and club-shaped forms. 

 It differs in size according to its culture 

 medium, hut is generally 3 or 4 ,« in 

 length. Cobbett and Graham-Smith re- 

 cognise five morphological types of diph- 

 theria bacilli on yoimg serum cultures: 

 — (1) Oval bacilli, with one unstained 

 septum ; (2) long, faintly-stained, irregu- 

 larly-beaded bacilli; (3) long, regularly- 

 beaded baciUi — " streptococcal " forms ; 

 (4) segmented bacilli ; and (5) uniformly- 

 stained bacilli. AU these forms are 

 longer than the pseudo-diphtheria bacilli, 

 more curved, and generally with clubbed fig. 24.— Diagram of Bacuius 

 ends. Their arrangement to each other diphtherial. 



is generally likened to Chinese characters. In the membrane 

 which is its strictly local habitat in the body — indeed, with the 

 exception of the secretions of the pharynx and larynx, and occasion- 

 ally in lymph-glands and the spleen, the bacillus is found practically 

 nowhere else in the body — it sometimes shows parallel grouping, 

 lies on the surface of the exudation, and is separated from 

 the mucous membrane by the fibrin. It is mixed with other 

 organisms, which are performing their part in comphcating the 

 disease, or are normal inhabitants of the mouth. The bacillus 

 possesses five negative characters: namely, it has no spores, no 

 threads, and no power of motility ; it does not liquefy gelatine, nor 

 does it produce gas. It is stained with Loffler's methylene blue, and 

 shows metachromatic granules and polar staining. It is generally 

 best to use the stain in dilute form. The favourable temperature is 

 blood-heat, though it will grow at room temperature. It is aerobic, 

 and, indeed, prefers a current of air. LofHer contrived a medium 

 for cultivation which has proved most successful. It is made by 

 mixing three parts of ox-blood serum with one part of broth contain- 

 ing 1 per cent, of glucose, 1 per cent, of peptone, and | per cent, of 

 common salt; the whole is coagulated. Upon this medium the 

 Klebs-LofHer bacillus grows rapidly in eighteen or twenty hours, 

 producing scattered, "nucleated," round, white colonies, becoming 

 yellowish. Horse serum is used by some bacteriologists instead of 

 ox serum. Lorrain Smith and Marmorek also devised excellent 

 serum media. The bacillus grows well in broth, but without 

 producing either a pellicle or turbidity; it can grow on the 

 ordinary media, though its growth on potato is not readily 

 visible; on the white of egg it flourishes extremely well. In a 

 moist condition, as a rule, the bacillus has a low degree of 



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