EELATION OF PATHOGENIC TO SEPTIC BACTERIA. 21 



whence a good deal of dust was blown into the laboratory. The 

 dust contained an enormous number of spores, especially of 

 bacilli, as was proved not only by the direct observation, but 

 also by the fact that every kind of nourishing fluid, Cohn's 

 nourishing fluid, hay infusion, beef broth, mutton broth, pork 

 broth, &c., previously sterile, when exposed to the air on such 

 windy days for a second became very difficult of sterilisation ; 

 boiling for ten minutes and sometimes fifteen minutes, or even 

 more, did not produce sterilisation. After forty-eight hours' 

 incubation the fluid was invariably swarming with bacilli. 



During July, August, and September, when days were 

 tolerably still, especially on rainy days, and there were no high 

 winds, test-tubes containing sterile nourishing fluid could be 

 kept open, i. e. the cotton-Avool plug could be altogether re- 

 moved under carbolic-acid spray for several seconds, and 

 without being subjected to boiling after this remained sterile at 

 a temperature of 35° C, only a relatively small percentage, 

 varying from five to seven, being lost by air organisms. This 

 is not at all an unsatisfactory result, considering that the 

 laboratory faced the hay market, and considering how easily a 

 contamination could occur under these conditions. But at a 

 time with high winds the contamination was so serious that 

 even prolonged boiling after exposure did not sterilise. This 

 is not to be wondered at if we remember that fluids containing 

 hay bacillus spores and some other bacillus spores require for 

 absolute sterilisation boiling extending up to and even over 

 half an hour (see Cohn's 'Beitrage,' ii Bnd., ii Heft). The 

 results obtained subsequently, when resuming my work, not 

 in the previous locality, but in the laboratory of the Brown 

 Institution, near Vauxhall, situated in a less contaminated 

 atmosphere, were very much more satisfactory. Comparative 

 experiments which I here made showed that exposing to the 

 air for half a minute sterile nourishing fluids contained in test- 

 tubes during windy weather yielded about 50 per cent, failures, 

 while exposing them to air under the carbolic- acid spray yielded 

 no failures in one series, it yielded 5 per cent, failures in 

 another series. 



