140 



EDWIN O. JORDAN 



These experiments show that at least in some cases the bacterial 

 gelatinases exhibit their maximum effect at temperatures consider- 

 ably above the optimum temperatures for the growth of the organism 

 that produces them. The enzyme activity may even be manifested 

 above the thermal death-point of the bacteria producing the enzyme 

 (cf . pyocyaneus gelatinase at 60 the thermal death-point of B. pyo- 

 cyaneus is 56 and Sp. Finkler- Prior). 



THE ACTION OF FORMALIN UPON LIQUEFIED GELATIN. 



Mavrojannis 1 has called attention to what he considers an impor- 

 tant fact, namely, that while formalin has a solidifying action upon 

 the gelatin liquefied by certain bacteria, the gelatin liquefied by other 

 bacteria remains permanently fluid, even when subjected to the influ- 

 ence of formalin for long periods. Mavrojannis explains the differ- 

 ence by supposing that different stages occur in the destruction of the 

 gelatin molecule, and that the kind of enzyme that is produced by 

 certain microorganisms stops short with the production of gelatoses 

 (hardened by formalin), while in other cases a different enzyme is 

 produced that continues the digestion to the formation of gelatin- 

 peptones (not hardened by formalin). In the former category are to 

 be put, according to Mavrojannis, St. pyog. aureus, St. pyog. albus, 

 B. anthracis, B. pyocyaneus, and Sp. cholerae, while in the latter 

 belong Sp. Denecke, Sp. Finkler- Prior , and Sp. Metchnikovii. 



I have used the same methods for hardening as those employed by 

 Mavrojannis, 2 namely, introduction of the liquefied cultures (gelatin, 

 10 per cent) into a tightly closed jar in the bottom of which is a 40 per 

 cent formalin solution; the gas liberated from this solution brings 

 about the hardening in a constant and uniform fashion. I have also 

 added to 2 c.c. of the liquefied gelatin five drops of formalin and then 

 placed the tubes in the formalin jar. The outcome is about the same 



1 Ztschr. }. Hyg., 1903, 45, p. 108 Op. cit., p. 109. 



