FOOD AND DRINK /I 



which new tissue is built up or old tissue is repaired. 

 The burning up or oxidation of the proteids may give rise 

 to heat. 



Experiment 20. To test for proteid with the white of egg. As 

 a type of a group of proteids let us take the white of an egg, or 

 egg albumin. Place a few drops of the raw white of egg in a test 

 tube. Dilute it with a tablespoonful of water. Heat it over a flame. 

 The mixture will soon begin to turn white, and become thicker, or, in 

 other words, to coagulate. 



Experiment 21. To show grain albumin or gluten. Take a small 

 mass of dough made of wheat flour ; tie it in a piece of cotton cloth 

 and knead it under water until all the starch is washed out. The 

 sticky, stringy mass remaining on the cloth is gluten, made up of 

 albumin, some of the ash, and fats. 



Experiment 22. To show milk albumin or casein. Heat a little 

 sweet milk in a test tube or basin. It will not coagulate or curdle. 

 Add a few drops of vinegar and gently stir. The milk curdles and 

 separates into a solid curd (casein, the chief proteid of milk and fat) 

 and a yellowish fluid (the whey). 



102. Starches and Sugars. The starches and sugars, also 

 called carbohydrates, contain carbon, hydrogen, and oxygen, 

 but no nitrogen. This class of foods forms a large part 

 of all those plants which are generally used as articles 

 of diet. 



The starches stand first in importance among the vari- 

 ous vegetable foods. Wheat, barley, oats, rye, rice, maize, 

 tapioca, arrowroot, sago, potatoes, etc., are rich in starch. 



The sugars are widely distributed substances and include 

 cane, grape, malt, maple, and milk sugars. Honey and 

 molasses are sugar foods. 



Cellulose is a carbohydrate that cannot be digested. Of 

 it the bark and the fibers of fruit, cereals, and vegetables 

 are composed. 



