The Volatile and Essential Oils are contained in minute quantity in a
very large number of animal and vegetable foods. They contribute in part
to the flavour of fruits. They are the cause of the pungency and aroma of
mustard, horse-radish, cloves, nutmegs, cinnamon, caraway seeds, mint,
sage and other spices. Onions contain a notable quantity. When extracted
the essential oils become powerful drugs. In moderate quantities they are
stomachic and carminative, in larger quantities irritant and emetic.
Condiments and spices not only add flavour to food, but stimulate the
secretion of gastric juice and peristaltic movement.

The Alkaloids most used are those of tea, coffee, kola-nut, cocoa, coca,
tobacco and opium. Although the two last are generally smoked, they must
be classed amongst the food adjuncts. It is of little consequence whether
their active principles enter the body by the mouth and saliva or the
lungs; their action on the blood and nervous system is the same.

The Extractives, as they are called, comprise a number of bodies of
varying nature. They especially exist in flesh and flesh extracts. Amongst
these are the purins. They will be treated at greater length hereafter.

Alcohol is to some extent a true food, but its stimulant and other
action quite overshadows any food value it may possess.

There are other bodies such as the resins and bitters. The active
principle of Indian hemp is a resin.

There is a great difference of opinion as to the extent to which
stimulants may advantageously be used. It is remarkable that amongst
nearly all nations, either alcohol in some form or one of the stronger