492 Transactions of the Canadian Institute. [Vol. VII. 



The following data are from cans poorly cleaned, {see Fig. i^), cans 

 washed in tepid water and then scalded — the best farm practice — and 

 cans washed in tepid water and then steamed for five minutes {see Fig. 



15)- 

 Bacterial Contents of Cans Cleaned in Various Ways. 



Number of Bacteria per c.c. of Can Washings. 



Poorly Cleaned 238,500 342,800 215,400 



618,000 806,000 510,000 



230,000 600,000 418,000 



Average. .442,000. 



Ordinary Method 89,000 84,000 26,000 



24,000 38,000 76,000 



1 5 ,000 44,000 9 3 ,000 



Average. . 54,300. -, 



Approved Method 1,100 1,800 890 



355 416 725 



Average 880. 



All cans should be constructed so as to facilitate cleaning. Stamped 

 pails, without seams, may now be purchased, but if seams are present 

 they should be examined to see that they are well flushed with solder. 

 The bottoms of all cans should be concave, and not convex, to expedite 

 cleaning. 



After thorough rinsing to remove organic matter, cans should be 

 washed in hot water, to which borax or soda may be added. After 

 washing, rinse with boiling water, and if available place the can over a 

 steam-jet for a few minutes. 



The Effect of Temperature. 



After the milk is infected with bacteria, the temperature at which 

 it is kept exerts an important influence on the rate of growth or multi- 

 plication of the bacteria in the milk. Freudenreich^^ obtained some 

 milk, which when delivered at his laboratory two and a-half hours after the 

 milking, had 9,300 germs per c.c. Samples were stored at 15°, 25' and 

 36" C. (or 59°, T"]^ and 95° F.), and the results were as follows per c.c: 



15^ 25^ 35° 



3 hours 16,000 18,000 30,000 



6 " 25,000 172,000 12,000,000 



9 " 46,500 1,000,000 35,280,000 



24 " 5.700,000 577,000,000 50,000,000 



