CORYNEBACTERIUM MALLEI. 385 



by means of Neisser's staining method for diphtheria 

 granules. True endogenous spores are never present ; all 

 previous positive statements to the contrary are errone- 

 ous. In old cultures clubbed, vesicular enlargements 

 which create the impression of involution forms are often 

 seen; also long threads, which sometimes exhibit true 

 branching (57, xn) in great abundance. See Semmer (C. 

 B. xviii, 68). Dissertation bv Erich Wolf, Wiirzburg, 

 1898, and Marx (C. B. xxv, 274). 



Staining Properties. — Somewhat difficultly with ordi- 

 nary stains; does not stain by Gram's method. For 

 staining the bacteria in sections, Nicolle's method is to be 

 recommended (Technical Appendix). 



Requirements as Regards Composition of Nutrient 

 Media, Supply of Oxygen, and Temperature. — Grows 

 best at incubator temperature (minimum, 25°; maximum, 

 40°). Prefers glycerin-agar to ordinary agar, but is not 

 particular. Grows well aerobically, poorly or not at all 

 anaerobically. 



Gelatin Plate. — (a) Natural size. Superficial and deep 

 colonies: Small, whitish, punctiform; also after a long 

 time they do not become essentially larger. The super- 

 ficial ones have a delicate, transparent halo (57, v). 



(6) Magnified sixty times. Superficial : Irregularly round- 

 ish ; scalloped, wavy margin ; shining white, transparent, 

 with wavy elevations and marked reflex. Old colonies 

 are more yellowish, especially in the center, with linear, 

 depressed markings. They are very similar to colonies of 

 B. typhi and putidum in the early stages (57, vm, e). 

 Deep : Roundish or oval ; sharply outlined ; in the center 

 delicately crumbly, at the outer part streaked. The 

 peripheral zone is sharply marked (57, vm). 



Gelatin Stab. — Stab : Thread-like ; sometimes faintly 

 granular, sometimes like a string of pearls ; gray. Sur- 

 face growth: Exceedingly delicate, perfectly transparent, 

 gray, with a ragged fringe, and of a dull luster (57, i). 



Agar. — Not distinguishable from Bact. coli ; entirely 

 non-characteristic (57, iv, vn). For a year we cultivated a 

 form of the Cory, mallei, which occurred spontaneously and 

 which produces rusty-brown colonies upon agar. This is 



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