SOURCES OF INFECTION IN THE STABLE. 63 



that the last traces of animal odor may disappear,* pro- 

 vided only that the can has not too small an opening. The 

 cooling has, however, still more important results. If the 

 temperature of the milk is lowered sufficiently, the de- 

 velopment of bacteria will be completely stopped. The 

 low temperature places these organisms in a torpid condi- 

 tion, during which they are unable to multiply or to bring 

 about fermentations. A proper cooling of the milk will 

 therefore greatly increase its keeping quality. By lowering 

 the temperature to 45 F. (7 0.), satisfactory results may 

 be obtained ; but it is safest in all cases to cool to a tempera- 

 ture of 39 F. (4 0.). 



If the milk is to be hauled to a creamery not too far 

 away, where it will be immediately cooled further or 

 separated, it is not necessary to cool below 50 F. (10 C.). 

 At this temperature the activity of the bacteria is generally 

 stopped, and the small increase that may happen during 

 the short interval will not cause any damage worth men- 

 tioning, especially if the milk is protected from being 

 heated during the transportation. Even a cooling to about 

 54 F. (12 C.) has often proved of great advantage. 



The matter will, however, stand differently if the milk 

 has to be hauled far, and if it is not protected from heat- 

 ing during the transportation. The cooling must then be 



* It lias been claimed that a simple aeration of the milk will have 

 a beneficial effect on its keeping quality but this is erroneous, as 

 shown by Cooke (Vermont Experiment Station Report 1892, p. 127) 

 and Wing (Cornell Experiment Station Bulletin No. 39; Powell 

 Aerator). Aeration with cooling, on the other hand, will increase 

 the keeping quality of the milk; see Wing, loc. cit; Plumb (Purdue 

 Experiment Station Bulletin No. 44); Hills (Vermont Experiment 

 Station Bulletin No. 27) ; Armsby, Waters, and Caldwell (Pennsyl- 

 vania Experiment Station Bulletin No. 20). W, 



