MICRO-ORGANISMS IN MILK 



329 



milking and sampling, growth accounts for the larger part of the 

 germs found. Accordingly, temperature control is the largest 

 factor in controlling germ life in city milk." 



After testing nearly 300 samples of Chicago market milk Jor- 

 dan and the writer found that the number of bacteria increases 

 steadily as the seasonal temperature rises. During April the aver- 

 age number of bacteria in all samples was 9,361,000 per cubic cen- 

 timeter, during May, which was relatively cool, 10,071,000, and 

 during June, 18,924,000. 



Lewis and Wright investigated the bacterial content of cream 

 and found that cream of 3.3 days' age delivered in summer con- 

 tained 462,600,000 bacteria per cubic centimeter, while in winter 

 after five days the number of bacteria was 134,800,000 per cubic 

 centimeter. 



These figures suffice to show the importance of keeping milk 

 cool during transportation. Prompt cooling immediately after 



Fig. 162. Milk-can jackets. 



Fig. 163. Standard 



shipping jacket. 

 (A. H. Barber Creamery Supply Co.) 



Fig. 164. Milk- 

 can jacket. 



production is not the only factor, but during subsequent trans- 

 portation means must be provided for keeping the temperature 

 low up to the time of consumption. This involves proper carry- 

 ing to the railroad station, suitable refrigerator cars, cooling facil- 

 ities on the delivery wagons, and, last but not least, keeping cool 

 in the home. 



During transportation to the railway station the cans can be 

 kept cool by covering them with moist jackets (Figs. 162-164), 

 the evaporating water reducing the temperature. At the station 

 the platforms should be enclosed, which is, unfortunately, not 

 common (Fig. 165). On ordinary railway platforms the milk 

 cans are exposed to the heating influence of sun and air, and if the 

 covers are not tight dust may gain access to the inside. An inex- 

 pensive shed would obviate these troubles in large measure. 



For supplies of large communities some of the milk may have 



