vegetables is digested in the same manner. The proteids of flesh, like
those of vegetables, are converted into peptone by the digestive
juices--taking the form of a perfectly diffusible liquid--otherwise they
could not be absorbed and utilised by the body. Thus the products of
digestion of both animal and vegetable proteids and fats are the same.
Formerly, proteid matter was looked upon as the most valuable part of the
food, and a large proportion was thought necessary for hard work. It was
thought to be required, not only for the construction of the muscle
substance, but to be utilised in proportion to muscular exertion. These
views are now known to be wrong. A comparatively small quantity of proteid
matter, such as is easily obtained from vegetable food, is ample for the
general needs of the body. Increased muscular exertion requires but a
slight increase of this food constituent. It is the carbohydrates, or
carbohydrates and fats that should be eaten in larger quantity, as these
are the main source of muscular energy. The fact that animals, capable of
the most prolonged and powerful exertion, thrive on vegetables of
comparatively low proteid value, and that millions of the strongest races
have subsisted on what most Englishmen would consider a meagre vegetarian
diet, should have been sufficient evidence against the earlier view.

A comparison of flesh and vegetable food, shows in flesh an excessive
quantity of proteid matter, a very small quantity of glycogen (the animal
equivalent of starch and sugar) and a variable quantity of fat. Vegetable
food differs much, but as a rule it contains a much smaller quantity of
proteid matter, a large proportion of starch and sugar and a small
quantity of fat. Some vegetable foods, particularly nuts, contain much
fat.

Investigation of the digestive processes has shown that the carbohydrates
and fats entail little strain on the system; their ultimate products are