146 



PLANTS WITHOUT CHLOROPHYLL 



or vegetable to be canned either in salt and water or with sugar 

 and water, either of which substances aids in preventing the growth 

 of bacteria. The time of boiling will be long or short, depending 

 upon the materials to be canned^ Some vegetables, as peas, beans, 

 and corn, are very difficult to can, probably because of spores of 

 bacteria which may be attached to them. Fruits, on the other 

 hand, are usually much easier to preserve. 4fter boiling for the 

 proper time, the food, now free from all bacteria, must be put into 

 jars or cans that are themselves absolutely sterile or free from 

 germs. This is done by first boiling the jars, then pouring the 

 boiling hot material into the hot jars and sealing them so as to 

 prevent the entrance of bacteria later. 



Uses of Canning. Canning as an industry is of immense im- 

 portance to mankind. Not only does it provide him with fruits 

 and vegetables at times when he could not otherwise get them, 

 but it also cheapens the cost of such things. It prevents the waste 



of nature's products at a time 

 when she is most lavish with 

 them, enabling man to store 

 them and ' utilize them later. 

 Canning has completely 

 changed the life of the sailer 

 and the soldier, who in former 

 times used to suffer from vari- 

 ous diseases caused by lack of 

 a proper balance of food. 



Pasteurization. Milk is one 

 of the most important food 

 supplies of a great city. It is 

 also one of the most difficult 

 supplies to get in good condi- 

 tion. This is in part due to 

 the fact that milk is produced 



Pasteurizing milk .^Why should this ^ Jong distances from the city 



and must be brought first from 



farms to the railroads, then shipped by train, again taken to the 

 milk supply depot by wagon, there bottled, and again shipped 



