TRANSPORTATION PROBLEMS. 177 
of its original bulk. Then the cream, which has also been sub- 
jected to the same heat, is replaced, making a product one-fourth its 
former weight. This milk has been pasteurized by the heat used in 
evaporation and is consequently free from disease bacteria. When 
the original amount of water is replaced it is indistinguishable from 
fresh milk. Concentrated milk will keep for several days without 
spoiling, and can be much more easily handled than ordinary milk. 
In still other preparations the water is almost wholly removed, pro- 
ducing milk powders, several different brands being on the market. 
They are prepared by various means, but in all the water is dried 
away from the milk, leaving a form that can be converted into a 
powder. Since they contain little water they will keep almost in- 
definitely. They have great use for special purposes, but are not 
a satisfactory substitute for fresh milk since they do not readily dis- 
solve again when water is added to them. 
Transportation. In the transportation of milk to market 
three factors are to be borne in mind: i. Cleanliness. This means 
that only thoroughly sterilized cans should be used to hold the milk, 
and that they should be completely closed, so as to avoid contamina- 
tion from without. The necessity for a complete sterilization of the 
milk cans cannot be exaggerated. 2. Temperature. If the milk is 
to be delivered in a good condition, it must be kept cold during 
transportation. This is accomplished fairly well by the ice car. 
3. Rapidity. The more quickly milk can be delivered to the cus- 
tomer, the better the result. But milk kept cold, below 45 F., may 
be delivered from 24 to 36 hours old and be in better condition 
than milk fresh from the farm, only five or six hours old, which has 
not been properly cooled. For this reason it not infrequently 
happens that milk brought in a milk cart, directly from the farm 
only a few miles distant from the consumer, is of poorer quality, so 
far as numbers of bacteria are concerned, than milk that has been 
brought long distances in a well iced milk car, though it may be 
36 or even 48 hours old. As an actual fact, milk furnished small 
communities near the source of the supply is frequently of poorer 
quality and, on the whole, less reliable than that furnished the 
larger cities. 
