1889.] Carbonic Anhydride, #., on Micro-organisms. 297 



(a.) With B. pyocyaneus. 



1st Experiment (March 19th, 1886). 



Air-plates CO-plates 



(after 4 days), (after 8 days). 



Number of colonies from 1 c.c. f (a.) 28,952 (a/) 0* 



of the mixture \ (6.) 27,794 (&.') 



* After three days' exposure to air, there were found on examina- 

 tion 



(a!) 20,558 colonies. 

 (V) 16,142 



2nd Experiment (March 29th, 1886). 



Air-plates CO-plates 



(after 4 days), (after 9 days). 

 Number of colonies from 1 c.c. 



of the mixture 6124 467* 



*After five days' exposure to air, 6333 colonies were found. 



3rd Experiment (April 10th, 1886). 



Air-plates CO-plates 



(after 4 days), (after 7 days). 



Number of colonies from 1 c.c. 



of the mixture 113,978 0* 



*In this experiment a dish with pyrogallic acid and caustic potash 

 was placed in the damp-chamber, in order to remove any trace of 

 free oxygen which might be present. After four days' subsequent 

 exposure to air, 100,821 colonies were found. 



From the above experiments, it is evident that carbonic oxide exerts 

 a very powerful influence on the vitality of B. pyocyaneus, for it 

 effectually stops their development, but that this is only a temporary 

 check to their growth is shown by the fact that on being removed to 

 a damp-chamber containing air, almost the same number of colonies 

 made their appearance as were found in the first instance on the air- 

 exposed plates. The results of the 2nd experiment suggest that in 

 this case there were possibly traces of air still remaining in the 

 chamber. 



(6.) With Koch's Comma Spirilla. 

 1st Experiment (March 29th, 1886). 



Air-plates CO-plates 



(after 4 days) . (after 9 days) . 

 Number of colonies from 1 c.c. 



of the mixture 100 48* 



* After five days' exposure to the air, the number of colonies rose 

 to 76. 



VOL. XLV. X 



