MICRO-ORGANISMS IN MILK 291 



The bacterial content of some foods has been investigated by 

 Esten and Mason. According to these authorities curing and 

 sweating of hay is a bacterial fermentation, accompanied by for- 

 mation of a layer of mold on the surface. The average number of 

 bacteria per gram of hay was found to be 16,800,000, and a mix- 

 ture of grass and rye contained 15,000,000 bacteria per gram. 

 In hay two-thirds of the moisture is lost during storage, so that 

 1 gram of hay equals in bacterial content about 3 grams of grass. 

 During storage of hay the number of bacteria diminishes due to the 

 disappearance of many varieties, but a few kinds increase. Lique- 

 fying bacteria decrease. The authors found Bacterium lactis acidi 

 (Streptococcus lacticus) in but one out of a total of 28 samples 

 examined. The following table shows the distribution of groups 

 of bacteria in hay (Esten and Mason) : 



DISTRIBUTION OF GROUPS OF BACTERIA IN HAY 



Total Acid Rapid Slow 



bacteria. formers. liquefiers. liquefiers. Miscellaneous. 



16,800,000 850,000 275,000 1,438,000 14,240,000 



Percent 5 1.6 8.5 85 



Distribution of hay in the stable evidently contributes its 

 quota of germ-laden dust to the air. This fact emphasizes the 

 necessity, mentioned before, of constructing the ceiling of tight, 

 dust-proof material and, if hay is stored in a loft above the stable, 

 to carry it into the stable from the outside, instead of lowering it 

 through a hole in the ceiling or through a chute. The contamina- 

 tion of the air from hay is decreased somewhat if it is cured in the 

 field before storage and if moistened before it is carried into the 

 stable. 



The relation of the predominant groups of bacteria in grass is 

 given by Esten and Mason as follows : 



DISTRIBUTION OF GROUPS OF BACTERIA IN GRASS 



Total bacteria. Acid formers. Liquefying bacteria. Miscellaneous. 



15.000,000 42,000 232,000 14,700,000 . 



Percent 3 15.5 81.5 



Swamp grass contains more bacteria than grass from meadows 

 that are located on elevated ground. Esten and Mason found 

 Bacterium lactis acidi in but 1 out of 9 samples examined. The 

 average number of liquefying bacteria was 50 per cent, greater 

 than on stored hay. Soil bacteria are well represented on grass, 

 but are not included in the estimations made from milk, as they 

 do not multiply on the media that are commonly used for deter- 

 mining the germ content of milk. 



Esten and Mason give the following number of bacteria on 

 grain food, sawdust which is sometimes used for bedding, and 

 dried blood: 



