EELATION OF PATHOGENIC TO SEPTIC BACTERIA. 17 



subjected to boiling for about five minutes. This I have found 

 to be sufficient to keep them sterile for ever after. This mix- 

 ture, which I will speak of as " sterile gelatine pork/' remains, 

 even in the smallest quantity, solid up to a temperature of 

 25^ C, a temperature generally sufficiently high for the growth 

 of bacteria. 



Koch {' Zur Unters. d. Pathog. Organ.,' p. 24) recommends 

 a mixture of gelatine and nourishing fluid in such proportions 

 that the gelatine amounts to about 2^ to 3 per cent., and he 

 states this to have served in a solid state for the cultivation of 

 bacteria, not only at the ordinary temperature of the room, but 

 at temperatures varying between 20° and 25° C. 



Now, no kind of gelatine which I have been able to lay hold 

 of has kept solid at a temperature of 20° — 25° C. in such per- 

 centage, nor as 5 per cent, mixture, not even as 7 5 per cent. 

 Ten per cent, mixture is the lowest that 1 have been able to 

 keep solid at such a temperature. It is true a good many bac- 

 terial organisms grow tolerably well in a temperature about 

 15° — 18° C, at which the 2^ — 3 per cent, gelatine mixture is 

 solid, but their growth is very slow. In some instances, e.g. 

 Bacillus anthracis, the growth progresses tolerably well, 

 but in others it is extremely slow. To make spores of hay 

 bacillus sprout at such a temperature is exceedingly difficult, 

 and so it is also with the spores of some other kind of bacilli. 

 I have seen bacilli which absolutely refuse to grow at such a 

 temperature. Of micrococci some grow well, others do not. 



It is clear, then, that if, as is the case in laboratory experi- 

 ments, one requires growth of a particular organism to take 

 place within a reasonable time, not to mention those cases in 

 which organisms do not grow at all at so low a temperature, 

 the above temperature, viz. 15° — 18° C, is not sufficiently 

 high, and it is necessary to use gelatine mixtures stronger than 

 2^ — 3 per cent. The above 11 per cent, mixture of gelatine 

 and pork keeps well and solid at 25° C, and at this tempera- 

 ture all bacteria that I have tried grow well and abundantly. 



Thus far I have been describing the manner in which I pre- 

 pared the nourishing material, viz. sterile pork broth and sterile 



VOL. XXllI. NEW SKR. B 



