CH. II] THE CHARACTERS OF BACTERIA 25 



months previously the strains had repeatedly given normal 

 sugar reactions. 



(6) "Passage " through an animal, or series of animals — by 



'successive injections into the blood, or into the peritoneal 



cavity, and subsequent re-cultivation from the heart's blood 



or peritoneal fluid — is known to modify the characters of 



bacteria in many cases. 



Fermenting power, by such means, may be greatly modified 

 {vide p. 57). Virulence, again, may in this way be markedly 

 increased towards some animals and diminished towards others 

 {vide p. 81). 



It is claimed that the pseudo-diphtheria bacillus can be 

 converted into the Klebs-Loeffler bacillus by passage through 

 rabbits (Lesieur, 1901), or through guineapigs (Ohlmacher, 

 1902). 



Adami, Abbott and Nicholson (1899) injected typical B. coli 

 into the circulation of a rabbit and obtained diplococcic forms 

 of the organism from the liver after death. They isolated from 

 ascitic fluid in another case similar diplococci which stained 

 irregularly and were non-motile, did not ferment sugars or 

 produce indol, and formed colonies on agar closely resembling 

 those oi S.pyogenes. By intraperitoneal passages through three 

 guineapigs these organisms were converted into typical B. coli. 



Schmitt (1911) claims to have so modified a strain of 

 B. paratyphosus (Fliigge) by passage through a calf that it 

 afterwards gave the agglutinative reactions of B. enteritidis 

 Gaertner. 



. Calves, monkeys, rabbits, guineapigs, rats, mice and birds 

 may all be used for this purpose. 



(c) A modification of the last-named method consists in 

 growing organisms in a celloidin sac within the body cavity 

 of an animal. Martin (1898) increased the virulence of a strain 

 of B. diphtheriae by growing it in a celloidin sac in the peri- 

 toneal cavity of a rabbit. 



{d) Growth in the living tissues of an animal host is 

 another method of inducing variation. It is only in the animal 

 body that the actinomyces produces its characteristic rays or 

 clubs (Bowlby and Andrewes, 1913). 



