848 BACILLUS 



resistant to heat, form alkali in litmus milk, and are generally non-pathogenic, 

 though sometimes they may be fatal to mice and even guinea-pigs on intraperitoneal 

 inoculation in fairly large doses. The classification of these organisms is at present 

 impossible ; they seem to range from avirulent variants of B. anthracis, on the 

 one hand, to virulent variants of B. suhtilis on the other. For some of the strains 

 which have been described, see Hueppe and Wood (1889), Hartleb and Stutzer 

 (1897), Schulz (1901), Bainbridge (1903), Wilamowski (1912), and Grierson (1928) ; 

 and for two useful reviews see Pokschischewsky (1914) and Poppe (1922). 



6. subtilis. 



Great confusion has prevailed, and in fact still prevails, over this organism. 

 It was described by Ehrenberg in 1838, who found it in hay infusion, as Vibrio 

 suhtilis, and by Cohn (1875a) as Bacillus suhtilis. Neither of the descriptions 

 was sufficiently full to enable the organism to be distinguished from others that 

 simulate it closely, and in consequence organisms that are almost certainly different 

 from Cohn's original bacillus have been identified with this organism. In an 

 extensive investigation of the Bacillus group, Lawrence and Ford (Ford 1916) in 

 America gave this name to an organism that differs in several important par- 

 ticulars from that given by Cohn. The bacillus described by the German workers is 

 fairly large, 3-4 jj, long by 1 // thick, may form threads, is actively motile, forms 

 anthrax-like colonies on agar, gives rise to a thick, wrinkled surface membrane 

 in broth, liquefies blood serum, and gives a thick, yellowish- white, creamy growth 

 on potato, later appearing as if strewn with dry, white granules. The bacillus 

 described by the American bacteriologists is one of the smallest of the aerobic 

 spore-bearing bacilli, is 2 /^ long by 0-4 fi broad, does not usually form threads, 

 is sluggishly motile, forms dry, hard, glassy colonies on agar, adherent to the 

 medium, gives rise to a thin branching scum in broth, later becoming more dense, 

 fails to liquefy blood serum, and on potato gives a luxuriant, warty, pink growth. 



According to Conn (1930), there are two different types of bacilli commonly called 

 B. suhtilis, one forming small spores which germinate equatorially (Marburg type), 

 the other forming larger spores showing polar germination (Michigan type). Conn 

 advances reasons to j^rove that the Marburg type is the original and genuine type, 

 while Soule (1932) maintains that the classical B. subtilis is represented by the 

 Michigan type. At the second international Microbiological Congress the Marburg 

 type was officially accepted as the type strain (St. John-Brooks and Breed 1937). 

 Unfortunately, however, evidence on serological and other grounds has since 

 been adduced by Lamanna (19406) to show that the Marburg type strain is really 

 a strain not of B. suhtilis but of B. vulgatus (see also Lamanna 1942, Knaysi and 

 Gansalus 1944). 



In the following summary of the properties of B. subtilis we have described 

 the small-celled type of organism showing equatorial germination of the spore, 

 which was in the mind of the bacteriological nomenclature committee of the 

 Congress. For some of its properties we have drawn on the description given 

 by de Soriano (lr935), Lamanna (1940a, b) and on our own personal observations. 



Variant colonies with different bacillary morphology have been described by a 

 number of workers. According to Soule (1928), there is a rough and a smooth type 

 closely simulating the corresponding type of B. anthracis (see p. 843). Graham 

 (1930), who, like Soule, probably worked mainly with strains of the Michigan type, 

 described four variants, two of which were motile and two usually non-motile. 



