THE MULTIPLICATION OF MICRO-ORGANISMS 237 



organisms, the different deleterious effect of carbonic 

 acid gas on the B. pyocyaneus, Koch's cholera bacillus, 

 and Finkler-Prior's bacillus when growing on gelatine 

 plates was shown very clearly ; the plates were poured 

 as usual, and the vessel containing them filled with gas. 

 The following are the results obtained with Koch's 

 bacillus : 



Cholera Bacillus exposed in Plate-culture to Carbonic Acid Gas 

 (Percy Frankland) 



Number of Colonies obtained from 1 c.c. of a Sterilised Water 

 attenuation of the Bacillus 



Air Tlatcs CO, Plates 



4,183 (after 4 days) l 



4,440 (after 5 days) 



1 These plates were then transferred to a damp chamber filled with air, and examined after 

 three days, but no colonies were found. 



Sohnke confirmee! the experiments of Leone, and 

 obtained a marked diminution in the number of bac- 

 teria in the water into which carbonic acid gas had 

 been introduced. This investigator also found that, 

 whereas the seltzer-water prepared from well-water 

 contained, although a smaller number of bacteria than 

 was originally present in the water, yet a considerable 

 quantity (200-6,600 per c.c.), the seltzer-water made 

 from distilled water contained only from ten to thirty 

 micro-organisms per c.c. Samples of the latter seltzer- 

 water, when kept from one to nine months, contained 

 still a few microbes, whilst three' samples, which had 

 been preserved from three to four years, were found to 

 be entirely free from micro-organisms. 



Pfuhl examined seltzer-water from two different 

 manufactories in Altona, in both of which the ordinary 

 Altona water-supply was used. In one case as many as 

 20,000 bacteria in a single c.c. were discovered, but 

 as this was the only bottle examined from the manu- 

 factory in question, possibly some accidental contami- 



