Contamination of Milk. 41 



dition, organisms retain their vitality for long periods of 

 time. The use of dry fodder, the bedding of animals with 

 straw adds greatly to the amount of dust particles, and 

 consequently to the germ life floating in the air, as seen in 

 Fig. 11. Taints in milk have frequently been traced to 

 infection arising from this source. 



FIG. 11. Effect of contaminated air. The number of spots indicate the col- 

 onies that have developed from the bacteria which f ell in 30 seconds on the sur- 

 face of the gelatin plate (3 inches in diameter). This exposure was made at time 

 the cows were fed. 



While the stable cannot be entirely freed from dust, yet 

 the effect of this factor can be greatly minimized by a little 

 forethought. Feeding before milking adds materially to 

 the germ content of the air, if feed is of dry character. If 

 moistened and given during milking, the same objection 

 does not inure. The following data collated by Harrison 

 shows number of bacteria per minute deposited in a 12-inch 

 pail. In Series A, the exposure was made during bedding; 

 in B, one hour after this operation. 



