530 
THE ANAEROBIC BACTERIA 
Products of Growth. — B. welchii does not produce a protein liquefying 
enzyme, although the organism softens gelatin incidental to its develop- 
ment in this medium. Tissier and Martelly/ however, state that an 
organism (B. perf ringens) , which is apparently identical with the Welch 
bacillus, produces a diastase of the tryptic type, as well as enzymes 
which hydrolyze, and then saponify fats. This question of the pro- 
teolytic activity of the Welch bacillus is an important one; the most 
probable explanation of the non-concordant results upon this point is 
that those observers who report extensive proteolytic powers on the 
part of the organism were dealing with cultures containing the Welch 
bacillus (which asserts itself in the carbohydrate media by a very 
vigorous fermentation) and a spore-forming anaerobe of the proteolytic 
Fig. 73. — Bacillus welchii, smear from liver of rabbit. X 1000. 
type (probably B. sporogenes, Metchnikoff), growing symbiotically.^ 
It may be stated dogmatically that B. welchii does not induce an enzy- 
mic liquefaction of gelatin. Simonds^ has studied the nitrogen metab- 
olism of several cultures of B. welchii and finds that the organisms are 
unable to induce more than minimal changes in protein as a result of 
their growth. Wolf and Harris^ have repeated the essential details of 
this work and have confirmed Simonds' findings. Casein is precipi- 
tated from milk cultures of B. welchii, but it is not digested to an 
appreciable extent. The organism acts rather upon the lactose of the 
medium. The gas formed from carbohydrates is principally a mixture 
of H and CO2; hydrogen is in excess in the proportion of approximately 
1 Ann. Inst. Pasteur, 1902, 16, 865. Tissier and Gasching: Ann. Inst. Pasteur, 
1903, 17, 540. 
* Several of these "pure mixed cultures" have been purified by various observers, 
using the modified Barbour single cell method ; the fermentative gas bacillus, separated 
from the proteolytic B. sporogenes, has failed to induce more than minimal proteolytic 
changes in purely protein media. B. sporogenes, obtained from such mixtures, is 
actively proteolytic under these conditions. 
^ Loc. cit., p. 44. 
4 Jour. Pathol, and Bacteriol., 1916-1917, 21, 386. 
