126 EDWIN O. JORDAN 



shaking.* The reactions given for the nutrient media are based on 

 the phenolphthalein neutral point. 



CONDITIONS OF GELATINASE FORMATION. 



Composition oj medium. One inquiry of obvious theoretical 

 interest is whether gelatinase is formed more abundantly in gelatin- 

 containing media than in media in which no gelatin is present. 

 Lauder Brunton and Macfadyen, 1 as the result of their studies, con- 

 cluded that "an enzyme is formed in meat broth which liquefies gela- 

 tin, and does so more surely and quickly than the enzyme formed in 

 gelatin itself." Fermi, 2 on the other hand, found that in general the 

 enzyme production in broth was less abundant than in nutrient gela- 

 tin. Recently Abbott and Gildersleeve 3 have stated that in their 

 observations "the enzyme content of completely liquefied gelatin cul- 

 tures was always marked, and was in general more marked for all 

 species than was the case with any of the other culture media used." 

 These authors attach importance to this finding as tending to support 

 the doctrine of the over-production by the cell of particular receptive 

 atom groups. In this sense the presence of gelatin in the culture 

 medium would be expected to cause a more active elaboration of gelat- 

 inase. The influence of gelatin is hence regarded by Abbott and 

 Gildersleeve as "stimulating bacteria to the active production of 

 liquefying enzymes. " 



My results do not show that gelatinase production in nutrient 

 gelatin always outstrips or exceeds the production in nutrient broth. 

 The following table illustrates the conditions observed in a series of 

 tests. 



The table shows: (i) that some cultures develop gelatinase more 

 quickly and abundantly in nutrient broth than in nutrient gelatin 

 prepared from the same lot of broth; (2) that other organisms pro- 

 duce more gelatinase in nutrient gelatin than in nutrient broth; (3) 

 that in other cases there is little difference. In one instance (B. 



* Somewhat similar methods have been employed by Fermi, Malfitano and others. Fermi (Arch. /. 

 Hyg., 1906, 55, p. 140) has recently expressed a preference for the use of solid gelatin in place of fluid 

 gelatin as a means of testing the action of these enzymes, but the disadvantages of his method seem to me 

 greater than those of the one here described. I have not found it difficult to obtain comparable results 

 when attention is paid to details of mixing, temperature, etc. Some of the experiments I have made 

 could hardly be carried out by the use of solid gelatin. 



1 Proc. Roy. Soc., 1889, 46, p. 542. * Jour. Med. Res., 1903, 10, p. 42. 



" Centralbl. /. Bakt., 1891, 10, p. 401. 



