cal condition or to some other cause, are not particularly
desirable food materials in their natural state, are quite nutritious
when cooked or otherwise prepared for consumption. It is also a matter
of common experience that well-cooked food is wholesome and appetizing,
whereas the same material poorly prepared is unpalatable. There are
three chief purposes of cooking; the first is to change the mechanical
condition of the food. Heating changes the structure of many food
materials very materially, so that they may be more easily chewed and
brought into a condition in which the digestive juices can act upon them
more freely, and in this way probably influencing the ease and
thoroughness of digestion. The second is to make the food more
appetizing by improving the appearance or flavour or both. Food which is
attractive to the eye and pleasing to the palate quickens the flow of
saliva and other digestive juices and thus aids digestion. The third is
to kill, by heat, disease germs, parasites or other dangerous organisms
that may be contained in food. This is often a very important matter and
applies to both animal and vegetable foods. Scrupulous neatness should
always be observed in storing, handling and serving food. If ever
cleanliness is desirable it must be in the things we eat, and every care
should be taken to ensure it for the sake of health as well as of
decency. Cleanliness in this connexion means not only absence of visible
dirt, but freedom from undesirable bacteria and other minute organisms
and from worms and other parasites. If food, raw or cooked, is kept in
dirty places, peddled from dirty carts, prepared in dirty rooms and in
dirty dishes, or exposed to foul air, disease germs and other offensive
and dangerous substances may easily enter it.

9. _Pecuniary Economy of Food._--Statistics of economy and of cost of
living in Great Britain, Germany and the United States show that at
least half, and commonly more, of the income of wage-earners and other
people in moderate circumstances is expended for subsistence. The
relatively large cost of food, and the important influence of diet upon
health and strength, make a more widespread understanding of the subject
of dietetics very desirable. The maxim that "the best is the cheapest"
does not apply to food. The "best" food, in the sense of that which is
the finest in appearance and flavour and which is sold at the highest
price, is not generally the most economical.