414 J. RUSSELL ESTY 



mild local infection occurs from which recovery takes place in 

 a very few hours or the pig remains inactive with no appetite 

 for several days. The injection causes local swelling which after 

 two to three days forms a large abscess and breaks, exposing the 

 abdominal wall. After the abscess opens the pig gains steadily, 

 recovering completely in the course of five to seven days, while 

 the abscess heals and leaves a clean scar. 



Cultures of Clostridium Welchii vary greatly in virulence. 

 All strains showing any virulence are pathogenic for guinea-pigs, 

 while some may not cause fatal infection in rabbits. The viru- 

 lence of a strain is increased by passage through the animal 

 body. The source from which an organism was isolated gives 

 no absolute clue as to its pathogenicity. However, of the 9 

 strains of Clostridium Welchii isolated from the feces of man all 

 have proven very highly pathogenic for guinea-pigs and in 

 relatively larger doses, are pathogenic for rabbits. Of the 12 

 from cow feces, 8 are non-pathogenic and 4 are highly pathogenic. 

 These 4 strains were isolated from 4 cows in the same herd. 



The milk cultures used in the test for pathogenicity showed 

 a difference in virulence. Of the 12 cultures tested, 8 were 

 pathogenic in varying degrees; 2 in twelve hours, 2 in forty-eight 

 hours, 1 in eighty hours, 1 in five days, 1 in nine days and 1 in 

 eleven days. Four cultures from milk were grown for twenty- 

 four hours in sterile milk instead of glucose broth before the 

 injection of the animal to see if different culture media would 

 effect the pathogenic result. Apparently growth in sterile milk 

 gives the same result as in glucose broth for the strain was non- 

 pathogenic under both conditions. 



Controls were run to check up the results in all cases. The 

 pathogenicity of spores of Clostridium Welchii was tested in five 

 cases and gave negative results. To assure the inoculation of 

 spores alone, the cultures containing spores were heated to 

 80° for fifteen minutes in order to kill all the vegetative forms 

 before the injection into the animal. The spore cultures tested 

 were taken from two strains of Clostridium Welchii, one from 

 human feces and the other from market milk, both being virulent 

 for guinea-pigs in the vegetative form. Four of the experiments 



