THE SANITARY CONDITION OF MILK 87 



In addition to carbon dioxide, other gases of a dif- 

 ferent character may be present iu milk and in 

 cheese making cause the curd to float : such as 

 hydrogen, wliich is given off in butyric acid fermen- 

 tation, and derivatives of the marsh-gas series of 

 gases. The gases in milk are a part of tlie products 

 formed by bacteria, and impure milk ^Iien made 

 into dairj' products may cause trouble, not only 

 from the gases present, but also from subsequent 

 action of the bacteria. 



80. The Keeping Qualities of Milk are directly 

 proportional to its germ content. Milks that have 

 been produced from healthy animals under the most 

 sanitary surroundings will contain but little dirt 

 and foreign matter carrying the microorganisms 

 which produce fermentation changes. Milks which 

 readilj^ become sour or undergo fermentation are un- 

 suitable for food purposes, as they indicate previous 

 contamination in some way. For infant feeding the 

 wholesomeness or sanitary condition of milk is of 

 more importance than its fat content. 



The microscope is frequently employed to deter- 

 mine the presence of dirt and foreign materials in 

 milk. A microscopic examination of the milk supply 

 of large cities shows that there is much to be desired 

 in the way of a better quality of milk for general 

 food purposes. The health of the consumer is jeop- 

 ardized by continued use of impure milk. 



