2 18 ILUNOIS DAIRYMEN'S ASSOCIATION. 



of gases, changes take place which do influence the milk one way or the 

 other. Of course it is easily understood that the gases which have been 

 determined can have only indirectly a bearing upon the fermentations of 

 the milk. The presence of carbon dioxide, of oxygen, or residual gases, 

 called usually nitrogen, signifies nothing especially so far as these gases 

 themselves are involved, but, when we find that the amount of carbon 

 dioxide is greatly diminished as we draw the milk from the udder as we 

 pass it over the aerator, in fact, as we agitate it more or less in the pres- 

 ence of air; farther, as we note at the beginning, the milk in the udder 

 contains no trace of oxygen but with the milking process the amount of 

 oxygen greatly increases, a,s when the milk is treated as recited, under 

 carbon dioxide, the oxygen continues to increase in amount; and, too, as- 

 we notice the changes in the amount of the residuel gas, we can readily 

 understand that there are marked alterations going on in the milk as it 

 passes through the various manipulations of the dairy. 



It is not desirable to look upon aeration as simply a process which 

 means the elimination of animal odor which may be regarded as a 

 mooted question or mooted process — it were better that aeration should 

 be looked upon as a means of gaseous interchange between the milk and 

 the air. Perhaps it is desirable to get rid of animal odors or taints, 

 resulting from physiological process or disease, yet to my mind the most 

 significant and most practical side of aeration is the fact that obnoxious 

 gases which permeate the air are as rapidly taken in or absorbed by the 

 milk as the oxygen and the nitrogen of the air and these gases act as» 

 substitutes for the carbon dioxide and animal odor which in turn leave the 

 milk and pass into the air. This free interchange of gases, i. e., the 

 gases of the air passing into the milk and the gases of the milk passing 

 into the air, results from the desire of Nature's law to create an equalib- 

 rium of bases; therefore, we are safe in saying that any odor prevailing 

 in the stable, in the dairy, or anywhere where milk is exposed, is quite 

 likely to pass into the milk, consequently milking should be carried out 

 in a pure air and milk should not stand in an impure atmosphere. Aera- 

 tion should be conducted where there are no contaminating gases. 



Another point concerning aeration which is of practical consequence 

 is the matter of time in aerating and temperature of aerating.. If the 

 same milk is colled down to a low temperature, the animal odor disappears 



