1889."] Carbonic Anhydride, <$<?., on Micro-organisms. 299 



found on the control air-plates, and on being transferred to the air- 

 chamber a further though slight increase was found on re-examina- 

 tion. 



In the case of the Finkler spirilla, about one-seventh of the total 

 number of colonies were developed, and on being transferred to the 

 air-chamber a further increase was observed, being about one-fifth of 

 the total number which had grown on the control air-plate. 



These results are tabulated below. 



Experiments with Nitrous Oxide. 



This gas was prepared by heating ammonium nitrate in a retort, 

 and purified by passing it through a small tower filled with slaked 

 lime, also through strong sulphuric acid and sterilised cotton-wool. 

 In all the experiments, a dish containing pyrogallic acid and caustic 

 potash was placed in the damp-chamber. 



(a.) With B. pyocyaneus (April 10th, 1886). 



Air-plate N 2 O-plate 



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

 Number of colonies from 1 c.c. 



of the mixture ............ 113,978 0* 



*0n being transferred to an air-chamber, there were found after 

 four days 89,368 colonies. 



(6.) With Koch's Comma Spirilla (April 10th, 1886). 



Air-plates N 2 O-pla(es 



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



v . . , . , r(a.) 2,800 (a'.) 903* 



JN umber ot colonies trom 1 c.c. ' 



*0n being placed in an air-chamber no further colonies were 

 developed on (a) plate, whilst on (6') after four days the number had 

 risen to 23,328. 



(c.) With Tinkler's Spirilla (April 10th, 1886). 



Air-plates 

 (after 3 days). (after 7 days). 



Number of colonies from 1 c.c. f (a.) 4574 "1 649* 



of the mixture i (6.) 4320 J 



*0n being transferred to an air-chamber there were found, after 

 two days, 816 colonies. 



x 2 



