FOOD AND WATER, STIMULANTS, ETC. 83 



and, therefore, if milk is allowed to stand, the oil will rise 

 to the surface, making the cream. After the cream is 

 taken off, the milk looks thinner and more transparent. 

 If all the cream could be removed from it, it would be 

 clear, like water. In making butter, the milk is churned 

 until all the oily particles are stuck together in a mass, 

 and the watery part is separated : this latter is called 

 buttermilk. 



COOKING. 



24. Animals eat their food raw. Men, even the most un- 

 civilized, cook much of it. Cooking is useful in three ways. 



L It renders food more digestible, 

 z. It, kills parasites in meats, and stops putrefaction. 

 s. It creates flavors which are attractive, and stimulating 

 to the digestion. 



25. Raw meat is not unpalatable: a fondness for it is 

 often acquired. A disease called trichinosis is caused by 

 eating pork, which contains a minute worm called a trich- 

 ina. This worm can not be recognized in pork without 

 a microscope. It is killed by cooking: smoking is not 

 sufficient. The disease is, therefore, found only among 

 those who have eaten raw pork. Tape-worms are also 

 acquired by eating raw pork and beef. 



26. We can not digest starchy foods, such as the grains 

 and vegetables, in sufficient quantity, unless we cook them. 

 By cooking, we soften them so that they can be easily 

 separated into fragments, and dissolved by the digestive 

 juices. Besides, we add to them, in cooking, various 

 articles, such as salt, fat, sugar, and spices, which improve 

 their taste. Flour is, in this way, made into bread, and 

 cake, and pastry of many kinds. 



