POTATOES AND OTHER STARCHY ROOTS AS FOOD. 17 
gists therefore speak of different food materials as being potentially 
alkaline, acid, or neutral. The body performs its work best when its 
condition is either neutral or slightly alkaline, and consequently, in 
the ordinary mixed diet, it is important to counteract the effect of 
the potentially acid foods like meats, eggs, and fish with potentially 
alkaline ones like vegetables and fruits. It has been estimated that 
a portion of potatoes large enough to supply the body with 200 
calories of energy (over half a pound) would counteract the acidity 
from a portion of meat yielding 100 calories (about If ounces). 
These conclusions are in accord with the old custom in families 
where living is simple of serving a goodly helping of potatoes &nd 
other vegetables in proportion to the helping of meat. 
Aside from these considerations, potatoes deserve their important 
place in the diet for other reasons. They are easy to cook and can 
be prepared in so many ways that they add variety to the list of vege- 
table dishes, especially in winter, when green vegetables are not com- 
mon. They have a mild, agreeable flavor acceptable to almost every- 
one and combining well with other foods, but not sufficiently pro- 
nounced to become tiresome. Owing to the ease with which they are 
grown and their abundant yield, they are usually a relatively cheap 
food. Considering all these advantages, it is not surprising that in 
the temperate regions of America and Europe they rank next to 
the breadstuffs as a source of carbohydrates in the diet. 
SWEET POTATOES. 
The plants known in the United States as sweet potatoes are called 
by botanists Impomwa batatas or Batatas edulis, and are probably 
natives of tropical America. They were introduced into Europe 
earlier than the white potato and were formerly so commonly grown 
in the warmer countries of Europe that when the white potato 
supplanted them the latter took its English name from a corruption 
of the usual European name of sweet potato — batatas. Since then, 
however, they have fallen out of use in Europe, it is said because 
they are considered too sweet for vegetables and not sweet enough 
to take the place of cakes, sweet fruits, etc. 
At present the sweet potato is grown throughout the Tropics and 
warmer temperate zones, being a well-known food crop in the south- 
ern part of North America, in Central America, and in the West 
Indies, Hawaii, and the Philippines. In the southern United States 
they play almost as important a role as white potatoes do in other 
parts of the country and have almost usurped the name potato. Al- 
though the name yam (see p. 23) belongs rightly to an entirely 
different tuber hardly known outside the Tropics, sweet potatoes 
are sometimes so called in the United States, particularly certain 
