EXPERIMENTS WITH BACTERIAL ENZYMES 141 



in the two procedures, except that the addition of formalin accelerates 

 the hardening process. The results may be stated briefly: 



Eight different species have been tested: B. pyocyaneus (nine 

 strains), B. anthracis, B. prodigiosus, B. subtilis, Sp. cholerae, Sp. 

 Finkler-Prior, Sp. Metchnikovii, and Sp. Denecke. In each case the 

 results were the same. Young gelatin cultures became solid in the 

 formalin jar, while older cultures of the same species remained fluid 

 even after exposure to the formalin vapor for three months. Cultures 

 grown at 20 always solidified sooner than those of the corresponding 

 age grown at 37. Different strains of the same microorganism gave 

 different results. For example, the gelatin liquefied by nine strains 

 of B. pyocyaneus, all grown at 20 for 21 days, hardened in formalin 

 in 24 hours in one case and in 48 hours in two cases, but was still fluid 

 after three months in the other six. The gelatin liquefied by a three- 

 day growth of B. prodigiosus at 20 solidified in three days, but the 

 15 day growth of the same organism remained fluid at the end of 

 three months. 



Mavrojannis 1 has even gone so far as to champion the action of 

 formalin upon liquefied gelatin cultures as a means of distinguishing 

 the cholera vibrio from other species. According to this writer, Sp. 

 cholerae manufactures a gelatinase which is capable of digesting gela- 

 tin only as far as the stage of gelatoses (solidifying in formalin), while 

 Sp. Metchnikovii, Sp. Denecke, and Sp. Finkler-Prior push the de- 

 composition to the gelatin-peptone stage (permanently liquid). An 

 experiment with the cultures of these organisms in the laboratory 

 collection gave the following results : 



EXPERIMENT. 

 A. 



Cultures grown at 20 for 10 days, then transferred to formalin jar; liquefaction 

 approximately the same in all. 



Sp. Denecke Hard in 24 hours 



Sp. Metchnikovii " " 48 " 



Sp. cholerae (Wherry, Manila) " " 14 days 



Sp. Finkler-Prior Not hard in 106 " 



B. 



Cultures grown at 37. 5 for 6 days, then transferred to formalin jar. 

 Sp. Denecke , 



^fitfcnLy.MMh) AUUquid after todays 

 Sp. Finkler-Prior 

 1 Jour, df physiol. et Path, ginir. 1904, 6, p. 273 



