646 Reading-Course for Farmers' Wives. 



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

 opening of six inches in diameter has an exposure of 28.26 square 

 inches. Figs. 167, 170. 



Milkers should get into the habit of using the small top pail as it is 

 one of the easiest of all ways for reducing the number of bacteria that 

 fall into milk. 



6. Contamination by flics. — A fly or a bit of hay or straw or a 

 piece of saw-dust or a small hair may carry enormous numbers of bac- 

 teria into milk as is shown by the following experiments : 



A living fly was introduced into 500 c.c. of sterile milk. The milk 

 was shaken one minute and it then contained 42 bacteria per c.c. After 

 24 hours at room temperature, it contained 765,000 bacteria per c.c, and 

 after 26 hours 5,675,000. 



Fig. 170. — Diagram shotving size of openings 

 in various kinds of milk pails. The large 

 circle at the left represents the common milk 

 pail. The others show the perpendicular ex- 

 posure in the new kinds of pails. 



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

 placed in 500 c.c. of sterile milk. The milk was shaken one minute and 

 it then contained 3,025 bacteria per c.c. After 24 hours at room tem- 

 perature it contained 3,412,500 bacteria per c.c. 



One piece of sawdust from the stable floor was put into 500 c.c. of 

 sterile milk. The milk was shaken one minute and its bacterial content 

 was then found to be 4,080 per c.c. After 24 hours at room temperature 

 it was 7,000,000 per c.c. 



A hair from a cow's flank was put into 500 c.c. of sterile milk. 

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

 After 24 hours at room temperature it contained 55,000 per c.c, and 

 after 36 hours, over 5,000,000 bacteria per c.c 



