The Farm Table. 643- 



sauce spilled on the stairs or on the cupboard shelf, and not soon wiped 

 up. Dust is always present in the house ; bacteria and molds are seldom 

 absent from that dust. Bacteria with the greasy dampness, soon produce 

 a sour or rancid dishcloth ; mold and moisture produces the mildewed 

 towel; the moldy shelf will soon fill the cupboards with odors. All such 

 articles furnish food for these dust-plants. 



11. THE CONTAMINATION OF MILK BY MEANS OF DUST. 

 Professor R. A. Pearson. 



Modern sanitation tries to eliminate dust, and to remove lodging 

 places for it. Dust-laden moldings and draperies are being eliminated 

 from houses. (See Reading-Course Bulletin 12, for Farmers' Wives.) 

 These ideas are now extending to the barns, and are beginning to revolu- 

 tionize barn construction and barn management. The first attention 

 should be given to the protection of milk. Dust is not only " dirt," but it 

 also carries germs or bacteria ; and all bacteria contaminate the milk and 

 many of them may produce distinct disease or disorder in the milk user. 



Very few and often no bacteria are found in the air over large bodies 

 of water. There is very little or no dust in such places. After a pro- 

 longed fall of rain or snow which has caused dust to settle, the air is 

 found to be almost or quite free from bacteria. In other words, bacteria 

 are most abundant in the air when dust is present. It is probably safe to 

 say that every particle of dust which floats in the air is carrying a greater 

 or less number of bacteria, just as a raft floating in the water may carry 

 a greater or less number of men. Tyndall suggested this long ago, and 

 the idea is called his " raft-theory." 



As has been shown, there is less dust (and therefore fewer bacteria) 

 over water surfaces than over land surfaces. There is little dust and few 

 bacteria at very high altitudes. A French investigator found no bacteria 

 in 100 liters of air at the top of Mount Blanc. But the examination of 

 air in an observatory at that point showed a small number of bacteria. 



There are fewer bacteria in country air than in city air. The reason 

 for this is understood when we remember the enormous traffic and the 

 continuous action taking place in the streets and elsewhere in the city. 

 Dust is being stirred up all the time. Furthermore, city dust is likely to 

 carry more objectionable kinds of bacteria than are carried by dust in the 

 country. 



There is more or less dust floating in the air of houses and stables, 

 and this dust is constantly settling. When it falls into milk it carries bac- 

 teria with it. If the milk is warm, these bacteria increase very rapidly; 

 if the milk is cold, they may develop slowly but will be ready for rapid 



