EXPERIMENT STATION BULLETINS. 



287 



XVI. THE ACTION OF 32.9 PER CENT OF CARBON DIOXIDE UPON THE DEVELOP- 

 MENT OF BACTERIA. 



TABLE XIV. 



119. 

 120. 

 121. 

 122. 

 123. 

 124. 

 125. 

 126. 

 127. 

 128. 

 129. 

 130. 

 131. 

 132. 

 133. 

 134. 



No. of micro-organism. 



Plates developed in 

 32.9% COs. 



Plates developed in 

 air as check. 



Growth. 



n. g. 

 v. g. 



V. g. 



v. g. 

 r- g- 

 v. g. 



No. of 

 colonies. 



2,880 



402 



1,540 



2,060 



!)00 



Growth. 



v. g. 

 v. g. 

 V. g. 

 V. g- 



v. g- 

 v. g- 



No. of 

 colonies. 



5,200 

 3,020 

 510 

 1,960 

 4,240 

 1,000 



n. g. 

 n. g. 

 v. g. 



412 



v- g. 

 v. g. 

 v. g. 



::.1(K) 

 :hmi 

 502 



r- g- 

 v. g. 

 n. g. 

 n. g. 

 r- g- 



1,420 

 1,800 



560 



v. g. 

 v. g. 

 v. g. 



V. g. 

 v. g. 



4S(> 

 1,720 

 1,800 

 1,520 



980 



v. g. of COi column is not so fully developed as v. g. in air and might be considered more correctly a 

 good growth. 



In most eases there is a vigorous growth which is noted in the table, yet this vigorous 

 growth is not so far advanced as that in the air plates. The action of carbon dioxide 

 is slight as compared with the preceding tables. While four out of fifteen have failed 

 to develop, still six of the previously retarded have developed vigorously. Xos. 123 

 and 130 which have been so susceptible to the action of free carbon dioxide now present 

 colonies of slow development only. The conclusion therefore to be drawn from this 

 table is the amount of carbon dioxide used approximates the border line between carbon 

 dioxide as it exists in an active form and where it begins to manifest little influence 

 upon the development of bacteria. 



It is noteworthy that the percentages of carbon dioxide which just inhibits stands so 

 near to the percentages of carbon dioxide obtained from milk after the aerating 

 methods have been employed as described in the foregoing pages. We are led to 

 believe that some relationship exists between the carbon dioxide content of milk and the 

 rate of fermentations evolved through the agency of bacteria. Tins conclusion will be 

 more strongrlv enforced in the tables which follow. 



