1934. (Bovine tubercle bacilli, Th. Smith, Trans. Assoc. Am. Phys., 11, 1896, 75; also see ibid., IS, 1898, 417; and Jour. Exp. Med., 3, 1898, 451; Mycobacterium tuberculosis ty- pus bovinus Lehmann and Neumann, Bakt. Diag., 4 Aufl., 2, 1907, 550; Mycobacterium tuberculosis var. bovis Berge}' et al., Manual, 4th ed., 1934,537.) bo'vis. L. noun bos the ox; L. gen. noun bovis of an ox. Common name: Bovine tubercle bacillus. Original description supplemented by ma- terial taken from Topley and Wilson (Prin- cip. of Bact. and Immun., London, 2nd ed., 1936, 315). Rods which are shorter and plumper than those of the human species. Range in size from 1.0 to 1.5 microns. Very short forms are frequently intermixed with somewhat larger forms. Stain regularly or irregularly. Acid- fast and acid-alcohol-fast. Gram-positive. Less easily cultivated than is the human species. Glj'cerol agar colonies: Small, irregular, with granular surface; no pigment. Dorset's egg, Lowenstein, Petragnani, Woolsey colonies: -Similar to those on glyc- erol agar, but growth is more rapid and colo- nies are somewhat larger. For variation in colony structure, see Mycobacterium tuberculosis. Glycerol broth: After 8 weeks, thin, gray- white film, slightly nodular; no turbidity; slight, granular deposit. Dubos' tween-albumin broth: Growth similar to that of M. tuberculosis. Optimum temperature, 37° C. Optimum pH, between 5.8 and 6.9 (Ishi- mori, Ztschr. f. Hyg., 102, 1924, 329); be- tween 6.0 and 6.5 (Dernby and Naslund, Biochem. Ztschr., 132, 1922, 392). Pathogenicity: Produces tuberculosis in ox, man, monkey, goat, sheep, pig, cat, par- rot, cockatoo and possibl}^ some birds of pre^^ Experimentally it is highly patho- genic for rabbits and guinea pigs, slightly pathogenic for dogs, horses, rats and mice; not pathogenic for fowls. Antigenic structure: See M. tuberculosis. Source: Isolated from tubercles in cattle. Habitat: The cause of tuberculosis in cattle. Transmissible to man and domestic animals. More highly pathogenic for ani- mals than is the human species. 10. Mycobacterium microti Reed, nom. nov. (Vole bacillus. Wells, Lancet, 1, 1937, 1221 ; Mycobacterium tuberculosis var. muris Brooke, Amer. Rev. Tuberculosis, 43, 1941, 806; Vole tubercle bacillus, Griffith, Jour. Hyg., 4^, 1942, 527; Mycobacterium muris Smith et al., in Zinsser's Textb. of Bact., 9th ed., 1948, 483; not Mycobacterium muris Simmons, Jour. Inf. Dis., 41, 1927, 13.) mic.ro'ti. M.L. mas.n. Microtus a genus that includes the vole; M.L. gen.noun microti of Microtus. Common name: Vole bacillus. Description taken from Brooke {op. cit., 1941, 806). Rods in cultures average 0.4 by 2.5 mi- crons and in tissues, 0.4 by 3.6 microns. Ovoid to spherical forms occasionally occur among the rods. In infected lymph nodes, rods 8 to 10 microns long are occasionally seen. Therefore resembles other mammalian acid-fast species, but in general longer and thinner. Irregular shapes are frequently found in tissues: S-shaped, hook-shaped, semicircular or circular. Acid-fast and acid- alcohol-fast. Growth in all media is slow; requires 4 to 5 weeks on favorable media before colonies are visible to the naked eye. Whole egg medium colonies: After 4 to 6 weeks, small, granular, with irregular mar- gins; on further growth the colonies become larger and more irregular. On moist media the consistency is creamj' and on dry media, butyrous to friable. Egg yolk-saline medium (3:1) : Growth on this medium is superior to that on Lowen- stein's, Dorset's egg or Dorset's egg plus extract of M. phlei. Growth is enhanced by the addition of 10 per cent CO2 to the at- mosphere. Nutrient broth without glycerol: Film- like colonies on the surface: fine deposit. Glycerol : Primary growth does not occur on any media containing glycerol. On sub- culture, growth occurs but is not enhanced by the presence of glycerol. Distinctive characters: Slow growth, slower than that of the human or bovine forms; growth in nutrient broth without
