196 MICRO-ORGANISMS AND DISEASE [chap. 



medium ascitic fluid made strongly alkaline ; then glycerine 

 is added, and the whole sterilised before inoculation with 

 the microbe. Incubating the cultivation at 37° C, it will 

 be found to have become completely solidified in forty-eight 

 hours, this solidification being due to neutralisation and 

 further coagulation of the alkali albumen. The same 

 phenomenon is observed with the typhoid bacillus sown in 

 the alkaline ascitic fluid and glycerine. So that both these 

 microbes are strong producers of acid; and yet there exists 

 this striking difference between the typical bacillus coli and 

 the typical bacillus of typhoid with which the above rapid 

 coagulation of alkali albumen is produced that the former 

 curdles milk in 36 — 48 hours while the latter does nothing 

 of the kind ; no coagulation of milk can be produced with 

 this particular typhoid bacillus that was used for the above 

 experiment. The conclusion which I think can be drawn 

 from these facts is that the curdling of the milk so con- 

 spicuous in the case of bacillus coli cannot be due solely 

 to the acid formed, but must be due to ferment action, and 

 further that those varieties of bacillus coli which have the 

 power of curdling milk in an imperfect degree (very late 

 curdling), or not at all, owe this deficiency to a want, not of 

 acid-production, but of ferment-production. A species of 

 non-sporing, non-liquefying aerobic bacillus occurs in a 

 small percentage of intestinal discharges and in a somewhat 

 larger percentage (30 per cent.) of sewage, which in so far 

 is of interest and importance as its distribution seems to be 

 limited to these two m.aterials ; at any rate I have not met 

 with them otherwise, and I have met with them in water 

 which had received in a conspicuous degree sewage, and for 

 this reason I am inclined to think that, if this species be found 

 in water, such water has most probably been polluted with 

 sewage ; and, further, I think the presence of this species in 



