Experiments with Bacterial Enzymes 125 



materially attenuating its gelatinolytic power. As a matter of fact, 

 Rietsch' in 1887 called attention to the existence of at least two 

 dfferent proteolytic ferments, and Fermi^ in 1891 pointed out that 

 the action of the bacterial ferments upon fibrin and egg albumin was 

 relatively feeble and was not correlated with their action upon gela- 

 tin.3 PoUak has recently stated that serum digestion and gelatin 

 digestion by trypsin solutions depend upon the action of two different 

 ferments. There is reason, therefore, for considering the gelatinases"* 

 as a definite class of bacterial proteases. According to Mavrojannis,^ 

 two kinds of gelatinases occur: (i) those that decompose gelatin 

 with the formation of gelatoses, and (2) those that push decomposi- 

 tion as far as the formation of gelatin peptones and perhaps beyond. 

 As will be shown presently, however, it is doubtful if this distinction 

 can be maintained. 



TECHNIQUE. 



In the work here described, a uniform procedure has been followed 

 in testing the gelatinolytic action of bacterial filtrates and cultures. 

 Five c.c. of neutral carbol gelatin (8.0 per cent gelatin; o. 25 per cent 

 phenol) has been used as the standard quantity to be subjected to 

 enzymic action; a measured quantity of the enzyme-containing fluid 

 is added to this while the gelatin is warm (35°-4o°) ; the control tubes 

 are diluted with 0.85 per cent NaCl solution correspondingly; en- 

 zyme and gelatin are thoroughly mixed by shaking, and incubation at 

 36°-37° for 20 hours follows. The tubes are then cooled in ice- water 

 for 1 5 minutes, after which they are removed and allowed to stand at 

 room temperature for 15 minutes, when the extent of solidification is 

 recorded. In case the action of the enzyme is complete, the contents 

 of each tube remain entirely liquid. I have termed the smallest 

 amount necessary to produce complete liquefaction under the condi- 

 tions specified the minimum lytic dose. If the action is only partial 

 the lower half or two-thirds of the gelatin may solidify, or the whole 

 mass may be semi-solid. Control tubes incubated for a similar 

 period show complete solidification without a trace of tremor on 



■ Loc. cil., p. II. 



' Cenlralbl. f. Bakl., i8gi, lo, p. 401. 

 J Beitrdge z. cliem. Physiol, u. Pathol., 1904, 6, p. 95. 

 « PoUak uses the term "glutinases ." 

 s Ztschr. /. Hyg., 1903, 45, p. 108; Compt. rend, de la Soc. de Biol. iqo», 55, p. 1605. 



