BACILLUS WELCH 1 1 527 
aiifl even in peptone meat-juice broth, sporiilation takes ])lace. B. 
welchii stains readily with ordinary aniHn dyes, and it retains the Gram 
stain both when observed in pathological tissue or fluids and in fresh, 
vigorously growing cultures. Older cultures, however, exliibit irregu- 
larities in staining and in their ability to retain the Gram stain. This 
phenomenon appears to be associated with degenerative changes in 
the organism. 
Isolation and Culture. — B. welchii is an obligate anaerobe. It grows 
well in ordinary media containing glucose or lactose, but soon dies, 
due apparently to the accumulation of products of fermentation. 
Growths from infected tissues are best obtained upon anaerobic serum 
or blood-agar plates. The colonies are round, semi-translucent, color- 
less and not distinctive upon the former, but surrounded by a double 
zone of hemolysis usually upon the latter. The majority of strains 
hemolyze blood, ^ and there is evidence that this property is a factor in 
inducing anemia both in naturally occurring and in artificially induced 
infections.2 McCampbelF states that the hemolytic action of B. 
welchii is caused by the acids formed during the growth of the organ- 
ism, and that carefully neutralized cultures do not therefore hemolyze. 
Other observers, however, have demonstrated a soluble hemolysin 
among the products of growth of the bacillus in artificial media.* The 
colonies on blood agar which exliibit hemolysis are surrounded usually 
by a double zone both of which are quite free from blood pigment. 
B. welchii is quite readily isolated from intestinal contents, the soil, or 
Avherever it exists in the spore state, through milk cultures. A suspen- 
sion of the suspected material is emulsified in whole milk, after the milk 
has been boiled, and cooled rapidly to exclude oxygen. The milk is 
heated after inoculation to 80° C. for twenty minutes to kill all vegeta- 
tive organisms, and then incubated at body temperature for eighteen to 
twenty-four hours. At the end of that time, or sooner, the medium 
exliibits a characteristic stormy fermentation. The casein appears as 
a faintly pink, fragmented mass, torn and riddled with gas holes, 
floating in a nearly clear whey. A ring of gas bubbles usually appears 
at the surface of the whey, and a faint but characteristic odor of butyric 
acid is readily detected. Pure cultures can be obtained from the whey 
by plating directly upon anaerobic ascitic fluid or serum agar, or by in- 
jecting some of the whey (a few cubic centimeters) into the ear vein of 
a rabbit. The rabbit is killed after five minutes, and placed in the 
incubator for twelve to eighteen hours.'' The rabbit will be found to be 
enormously distended with gas. The tissues, especially the muscles, 
will be found to be rather pale, friable, and greatly distended by a true 
gas edema. The course of the bloodvessels will be marked out by rows 
1 Herter: Jour. Biol. Chem., 1906-1907, 2, 1. Kamen: Centralbl. f. Bakteriol., 
orig., 1904, 35, 554, 686. Simonds: Loc. cit. 
2 Klotz and Holman: Jour. Infec. Dis., 1911, 9, 251. Schultzo: Virchow's Arch. f. 
path. Anat., 1908. 193, 419. 
3 Jour. Infec. Dis., 1909, 6, 537. " Simonds: Loc. cit., p. 13. 
^ This procedure is frequently referred to as the Welch-Nuttall t?st. 
