Contamination of Milk. 33 



or tuberculosis, in which case bacteria find their way di- 

 rectly into the milk. Marshall 1 succeeded in isolating 

 direct from the udder, a pure culture of Nocard's strep- 

 tococcus, the cause of infectious udder inflammation. 



The hairy coat of the animal offers exceptional facili- 

 ties for the harboring of dust and dirt. Cows wading in 

 stagnant pools cover the udder with slime and dirt that 

 is readily dislodged when dried. The hairy coat is, there- 

 fore, extremely rich in the various forms of bacterial life 

 that are derived from the particles of excreta that stick 

 to the flanks and under parts of the animal. Where peat 

 is used for bedding, favorable reports are made as to its 

 value. 



The amount of actual impurities that are to be found 

 in milk, even after it is strained, will surprise the casual 

 observer, although it should be noted according to 

 Backhaus, 2 that about one-half of fresh manure dis- 

 solves in milk and thus does not appear as sediment. 

 From a large number of determinations of the solid im- 

 purities found in the market milk of different European 

 cities, Renk 3 deduces the following rule: If a sample of 

 milk shows any evidence of impurity settling on a trans- 

 parent bottom within two hours, it is to be regarded as 

 containing too much solid impurities. These solid par- 

 ticles, composed largely of manure and dirt, are always 

 teeming with bacteria, especially with putrefactive and 

 decomposition organisms. It has recently been estimated 

 that the city of Berlin consumes daily 300 pounds of dirt 

 and filth in its milk- supply. 



Not only is the number of bacteria thus introduced into 

 the milk very considerable, but the character of the same 



1 Marshall, Mich. Expt. Stat., Bull. 146, p. 6. 

 'Backhaus, Milch Ztg., 26: 357, 1897. 

 3 Renk, Cent. f. Bakt., 10: 193. 

 3-B. 



