276 STATE BOARD OF AGRICULTURE. 



wiring a rubber tube about tbe neck of the flask and allowing it to reach above the 

 rubber stopper where it was cut off. This formed a cup shaped envelope for the stopper 

 and could be filled with mercury to cover the rubber stopper completely. Through the 

 glass tube the air-content of the flask could be removed easily at will and analyzed 

 without the possibility of extraneous air entering. 



Six analyses of air from different flasks made within a period of six weeks showed 

 no appreciable difference from that of the extraneous air used as check. 



IX. 'ACTION OF SPECIFIC MICRO-OBGANISMS UPON THE INTERCHANGE OF GASES 



BETWEEN MILK AND AIR. 



It becomes necessary, after a review of the gas-content of milk when unexposed to 

 the air, when exposed to the air by milking, and by the process of aeration, to consider 

 what influences fermentation may have. 



Of course it is well understood that micro-organisms are capable of producing different 

 gases, yet we have felt it obligatory to make some specific studies in this connection. 

 Consequently several micro-organisms isolated from milk and known by their labora- 

 tory numbers were used to inoculate sterilized milk and the flasks sealed as described 

 under V. 



It will at once be recognized that no attempt has been made to determine any other 

 gases which may be present than carbon dioxide and oxygen because with these alone 

 are we mostly concerned. Hydrogen and marsh gas were determined in several instances 

 and the results obtained were included with the total residual gas. 



In most analyses, it is worthy of emphasis, there have been noticeable decreases in 

 the amount of oxygen and increases in carbon dioxide. This, however, is not universally 

 true because in No. 121 there has been no production of carbon dioxide and the oxygen 

 has been but little reduced. In No. 126 there are no traces of carbon dioxide and still 

 the oxygen has been practically consumed. In short there is a wide diversity of 

 action, each micro-organism seems to be governed by its own peculiar functions. As a 

 rule, however, there seems to be sufficient proof that carbon dioxide is a common 

 product of these micro-organisms and that oxygen is consumed to a greater or less 

 degree. 



* See description of bacteria on page 2S4. 



