The Chemistry of Food and Nutrition | Page 5

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 water and carbon dioxide, which are easily disposed of.
The changes which the proteids undergo in the body are very
complicated. There is ample provision in the body for their digestion,
metabolism, and final rejection, when taken in moderate quantity, as is
the case in a dietary of vegetables. The proteids in the human body,
after fulfilling their purpose, are in part expelled in the same way as the
carbohydrates; but the principal part, including all the nitrogen, is
expelled by the kidneys in the form of urea (a very soluble substance),
and a small quantity of uric acid in the form of quadurates.
There is reciprocity between the teeth and digestive organs of animals
and their natural food. The grasses, leaves, &c., which are consumed by
the herbivora, contain a large proportion of cellulose and woody tissue.
Consequently, the food is bulky; it is but slowly disintegrated and the
nutritious matter liberated and digested. The cellulose appears but

slightly acted upon by the digestive juices. The herbivora possess
capacious stomachs and the intestines are very long. The carnivora
have simpler digestive organs and short intestines. Even they consume
substances which leave much indigestible residue, such as skin,
ligaments and bones, but civilised man, when living on a flesh dietary
removes as much of such things as possible. The monkeys, apes, and
man (comprised in the order _Primates_) have a digestive canal
intermediate in complexity and in length to the herbivora and carnivora.
A certain quantity of indigestible matter is necessary for exciting
peristaltic action of the bowels. The carnivora with their short intestinal
canal need the least, the frugivora more, and the herbivora a much
larger quantity. The consumption by man of what is commonly called
concentrated food is the cause of the constipation to which flesh-eating
nations are subject. Most of the pills and other nostrums which are used
in enormous quantities contain aloes or other drugs which stimulate the
action of the intestines.
Highly manufactured foods, from which as much as possible of the
non-nutritious matter has been removed is often advocated, generally
by those interested in its sale. Such food would be advantageous only if
it were possible to remove or modify a great part of our digestive canal
(we are omitting from consideration certain diseased conditions, when
such foods may be useful). The eminent physiologist and bacteriologist,
Elie Metchnikoff, has given it as his opinion that much of man's
digestive organs is not only useless but often productive of
derangement and disease. In several cases where it has been necessary,
in consequence of serious disease, to remove the entire stomach or a
large part of the intestines, the digestive functions have been perfectly
performed. It is not that our organs are at fault, but our habits of life
differ from that of our progenitors. In past times, when a simple dietary
in which flesh food formed little or no part, and to-day, in those
countries where one wholly or nearly all derived from vegetable
sources and simply prepared is the rule, diseases of the digestive organs
are rare. The