752 PATHOGENIC MICROORGANISMS 



On the other hand, it must also be stated that B. Welchii was fre- 

 quently present in wounds which never developed gangrene. Taylor 

 reports that B. Welchii was found in 80 per cent of all wounds 

 examined and that only 10 per cent of these developed gas gangrene. 

 The development of gas gangrene depends on the virulence of the 

 strain of B. Welchii, the amount of dead tissue present, and the 

 anaerobic conditions in the wound. In war wounds B. Welchii was 

 practically never present in pure culture. It was usually associated 

 with aerobes and with other anaerobes of the saccharolytic and 

 the proteolytic type. 



B. Welchii was discovered independently in three countries. It 

 was first discovered by Welch and Nuttall 6 in 1892, and called by 

 them Bacillus aero genes capsulatuSj a name still used by the majority 

 of English writers. In this country this organism is usually called 

 B. Welchii. Welch isolated it from the blood and organs of a cadaver 

 dead eight hours. In 1893 Fraenkel 7 isolated a similar organism in 

 Germany from several cases of gaseous phlegmons, calling it B. Phleg- 

 monis enephysematosae, but soon recognized that he was working with 

 the same bacillus previously described by Welch. However, this 

 organism is still referred to as the Fraenkel bacillus in German litera- 

 ture. In 1897, without having heard either of Welch's or FraenkePs 

 work, this organism was again described by Veilon and Zuber 8 in 

 France and called by them B. perfringens, B. Welchii, Bacillus 

 aerogenes capsulatus, Fraenkel bacillus, B. perfringens are all names 

 for the same organism. 



B. Welchii is a short, square Gram-positive bacillus, occurring 

 singly or in pairs. Chains are not formed as a rule. It is non-motile 

 and has a capsule. It grows best under strictly anaerobic condi- 

 tions, but its requirements for anaerobiosis are less rigid than those 

 of tetanus. It grows well in media containing tissue such as cooked 

 meat medium after simple boiling. With milk boiling is not always 

 sufficient to obtain good growth, and it is best to put milk tubes 

 in anaerobic jars. The majority of strains do not form spores 

 readily. Alkaline sugar-free media rich in protein, such as alkaline 

 egg, are necessary to demonstrate spore formation with the majority 

 of strains. The spore of B. Welchii is large, oval, and central or 



6 Welch and Nuttatt, Bull. Johns Hopkins Hosp., 3, 1892, 81. 



7 Fraenkel, Cent. f. Bakt., Bd. 13, 1893, 13. 



8 Veillon and Zuber, Arch, de Med. Exper., 10, 1898, 517. 



