f 98 Prof. P. F. Frankland. Influence of [Jan. 24, 



2nd Experiment (April 10th, 1886). 



*In these experiments pyrogallic acid was employed. The plates 

 were exposed afterwards during four days to the air, but on sub- 

 sequent examination the number of colonies was not found to have 

 increased. 



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



Air-plates CO-plates 



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

 Number of colonies from 1 c.e. f (a.) 45741 o# 



f 

 \ 



of the mixture ............ \ (6.) 4320 J 



*In this experiment pyrogallic acid was employed. After fonr 

 days' exposure to the air, the number of colonies rose to 501. 



In the carbonic oxide atmosphere, therefore, only a fraction of 

 Koch's comma spirilla, and a still smaller fraction of Finkler's 

 spirilla are developed ; the subsequent growth on exposure to the 

 air is relatively small, and in the case of Koch's comma spirilla prac- 

 tically nil. 



IV. Experiments with Nitrous Oxide, Nitric Oxide, Sulphuretted 

 Hydrogen, and Sulphurous Anhydride. 



Similar experiments were made with these gases. Those plates 

 which were exposed to an atmosphere of nitric oxide, sulphuretted 

 hydrogen, or sulphurous anhydride developed no colonies, neither 

 were any found on subsequently placing the plates in air-chambers. 

 These three micro-organisms are, therefore, rapidly destroyed by the 

 action of these gases. 



In the experiments with nitric oxide, the air was first driven out 

 of the damp- chamber with hydrogen in order to prevent the formation 

 of nitrous acid. 



The organisms behaved, however, differently in the presence of 

 nitrous oxide; in the chambers which were filled with this gas, and 

 in which pyrogallic acicl was also present, the Bacillus pyocyaneus 

 developed no colonies, but afterwards on being placed in an air- 

 chamber, almost as many colonies were found as were present in the 

 original control air-plates. 



Under similar circumstances, Koch's comma spirilla developed 

 in an atmosphere of nitrous oxide nearly one-third of the colonies 



