146 Physiology. 



Potatoes. Potatoes contain about twenty per cent starch, 

 two per cent of proteid, and no fat, the remainder being 

 chiefly water, with some useful salts, especially potash salts. 

 In spite of its relatively low food value, the potato is our 

 most useful vegetable on account of its abundance, the ease 

 with which it can be preserved, and the readiness and the 

 variety of ways in which it can be cooked. 



Other Vegetables. The chief nutrient in vegetables is 

 starch, though in many the starch is present in small amounts. 

 The salts and acids present are of value, and care should 

 be observed not to remove too much of these salts in cook- 

 ing. The fibrous matter, cellulose, while indigestible, is of 

 value in adding bulk to the mass of food to be digested. 



Scurvy. Formerly sailors were subject to scurvy; this 

 is now attributed to a diet of fat and salt meat, to the 

 exclusion of fresh vegetables, etc. The disease is avoided 

 by a greater use of vegetables, lime juice, etc. 



Fruits. Ma.ny of the fruits, such as bananas and 

 apples, have considerable starch and sugar. But the 

 fruits are more useful to us on account of their flavor, 

 due to aromatic bodies, and to their salts and the peculiar 

 fruit acids. 



Water. Water constitutes about two thirds of the 

 entire weight of the body. It constitutes the bulk of the 

 liquids we have studied, blood, lymph, sweat, saliva, bile, 

 etc. Water dissolves and carries all the material of the 

 body. Hence we need a large amount of it ; of course we 

 must remember that we get a good deal of water in most 

 of our solid foods. 



Rain Water. Water, as it comes from the clouds, is 

 pure. After enough rain has fallen to wash the air, rain 



