i39° The Cornell Reading-Courses 



square inches; a pail with 12-inch top has an opening of 113.04 square 

 inches; one with 10-inch top has an opening of 79.79 square inches; a pail 



with an opening of 6 inches 

 in diameter has an exposure 

 of 28.26 square inches. 



' Milkers should get into 

 the habit of using the small- 

 top pail, as it is one of the 



Fig. 29.— Diagram showing size of openings in easiest of all ways for reduc- 

 various kinds of milk pails. The large circle , , r , 



at the left represents the common milk pail. m K the number Ot bacteria 

 The others show the perpendicular exposure in that fall into milk. 

 the new kinds of pails (/ , . . _ . 



6. Contamination by flies. — 



A fly or a bit of hay or straw or a piece of sawdust or a small hair, may 

 carry enormous numbers of bacteria into milk as is shown by the follow- 

 ing experiments: 



"A living fly was introduced into 500 cubic centimeters of sterile milk. 

 The milk was shaken one minute and then it contained 42 bacteria per 

 cubic centimeter. After 24 hours at room temperature, it contained 

 765,000 bacteria per cubic centimeter, and after 26 hours 5,675,000. 



7. " Dirt in the milk. — A piece of hay about two inches long was placed 

 in 500 cubic centimeters of sterile milk. The milk was shaken one minute 

 and it then contained 3,025 bacteria per cubic centimeter. After 24 hours 

 at room temperature it contained 3,412,500 bacteria per cubic centimeter. 



" One piece of sawdust from the stable floor was put into 500 cubic 

 centimeters of sterile milk. The milk was shaken one minute and its 

 bacterial content was then found to be 4,080 per cubic centimeter. After 

 24 hours at room temperature it was 7,000,000 per cubic centimeter. 



"A hair from a cow's flank was put into 500 cubic centimeters of sterile 

 milk. After shaking the milk for one minute it contained 52 bacteria per 

 cubic centimeter. After 24 hours at room temperature it contained 55,000 

 per cubic centimeter, and after 36 hours over 5,000,000 bacteria per cubic 

 centimeter." 



references for further study 

 Belcher, S. D. Clean milk. Hardy Publishing Company, New York. 

 Conn, H. W. Agricultural bacteriology. P. Blakiston's Son & Co. 



'■ The story of germ life. D. Applcton & Co., New York 



Bacteria, yeasts, and molds in the home. Ginn & Co. 



Practical dairy bacteriology. Orange Judd Company, 



New York 

 Elliott. Household bacteriology. American School of Home Economics, 



Chicago 

 Lipman. Bacteria in relation to country life. The Macmillan Company 

 Marshall. Microbiology. P. Blakiston's Son & Co. 



