VEGETARIANS AND THEIR TEETH
No mistake, said Huxley, is more frequently made by clever people than
that of supposing that a cause or an opinion is unsound because the
arguments put forward in its favour by its advocates are foolish or
erroneous. Some of the arguments put forward in favour of the
exclusive use by mankind of a vegetable diet can be shown to be based
on misconception and error, and I propose now to mention one or two of
these. But I wish to guard against the supposition that I am convinced
in consequence that animal substances form the best possible diet for
man, or that an exclusively vegetable diet may not, if properly
selected, be advantageous for a large majority of mankind. That
question, as well as the question of the advantage of a mixed diet of
animal and vegetable substances, and the best proportion and quantity
of the substances so mixed, must be settled, as also the question as
to the harm or good in the habitual use of small quantities of
alcohol, by definite careful experiment by competent physiologists,
conducted on a scale large enough to give conclusive results. The
cogency of the arguments in favour of vegetarianism which I am about
to discuss is another matter.
In the first place it is very generally asserted by those who advocate
a purely vegetable diet that man's teeth are of the shape and pattern
which we find in fruit-eating or in root-eating animals allied to him.
This is true. The warm-blooded hairy quadrupeds which suckle their
young and are called "mammals" (for which word perhaps "beasts" is the
nearest Anglo-Saxon equivalent) show in different groups and orders a
great variety in their teeth. The birds of to-day have no teeth, the
reptiles, amphibians, and fishes have usually simple conical or
peg-like teeth, which are used simply for holding and tearing. In some
cases the pointed pin-like teeth are broadened out so as to be
button-like, and act as crushing organs for breaking up shell-fish.
The mammals alone have a great variety and elaboration of the teeth.
[Illustration: Fig. 21.--Side view of the skull of a clouded tiger
(_Felis nebulosa_) to show the teeth. _inc. s._ The three incisors.
_can. s._ Upper canine, corner-tooth, or dog-tooth. _can. i._ Lower
canine. _m. s._ The four upper molars or cheek-teeth (called
"grinders" in herbivorous animals). _m. i._ The three lower molars or
cheek-teeth.]
[Illustration: Fig. 22.--View in the horizontal plane of the teeth of
the lower and upper jaw of the same clouded tiger's skull. _inc. i._
Lower incisors. _inc. s._ Upper incisors. _can. i._ and _can. s._
Lower and upper canine. _m._ The cheek-teeth--three only in the lower
jaw, a minute fourth molar present in the upper.]
In shape and size, as well as in number, the teeth of mammals are very
clearly related to the nature of their food in the first place, and
secondly to their use as weapons of attack or of defence. When the
surface of the cheek-teeth is broad, with low and numerous tubercles,
the food of the animal is of a rather soft substance, which yields to
a grinding action. Such substances are fruits, nuts, roots, or leaves,
which are "triturated" and mixed with the saliva during the process
of mastication. Where the vegetable food is coarse grass or tree
twigs, requiring long and thorough grinding, transverse ridges of
enamel are present on the cheek-teeth, as in elephants, cattle, deer,
and rabbits (see Figs. 8, 17, 19). Truly carnivorous animals, which
eat the raw carcases of other animals, have a different shape of
teeth. Not only do they have large and dagger-like canines or
"dog-teeth" as weapons of attack, but the cheek-teeth (very few in
number) present a long, sharp-edged ridge running parallel to the
length of the jaw, the edges of which in corresponding upper and lower
teeth fit and work together like the blades of a pair of scissors. The
cats (including the lions, tigers and leopards) have this arrangement
in perfection (see Figs. 21 and 22). They cut the bones and muscles of
their prey into great lumps with the scissor-like cheek-teeth, and
swallow great pieces whole without mastication. Insect-eating mammals
have cheek-teeth with three or four sharp-pointed tubercles standing
up on the surface. They break the hard-shelled insects and swallow
them rapidly. The fish-eating whales have an immense number of
peg-like pointed teeth only. These serve as do those of the
seals--merely to catch and grip the fish, which are swallowed whole.
It is quite clear that man's cheek-teeth do not enable him to cut
lumps of meat and bone from raw carcases and swallow them whole, nor
to grip live fish and swallow them straight off (Pl. VI). They are
broad, square-surfaced teeth, with four or fewer low rounded tubercles
fitted to crush soft food, as are those of monkeys (see Pl. VII and
its description). And there can be no doubt that man fed originally,
like monkeys, on easily crushed fruits, nuts, and roots. He could not
eat like a cat.
A fundamental mistake has arisen amongst some of the advocates of
vegetarianism by the use of the words "carnivorous" and "flesh-eating"
in an ill-defined way. Man has never eaten lumps of raw meat and bone,
and no one proposes that he should do so to-day. Man did not take to
meat-eating until he had acquired the use of fire, and had learnt to
cook the meat before he ate it. He thus separated the bone and
intractable sinew from the flesh, which he rendered friable and
divisible by thorough grilling, roasting, or baking. To eat meat thus
altered, both chemically and in texture, is a very different thing
from eating the raw carcases of large animals. Man's teeth are
thoroughly fitted for the trituration of cooked meat, which is,
indeed, as well suited to their mechanical action as are fruits, nuts,
and roots. Hence we see that the objection to a meat diet based on the
structure of man's teeth does not apply to the use of cooked meat as
diet. The use by man of uncooked meat is not proposed or defended.
Yet, further, it is well to take notice of the fact that there are
many vegetarian wild animals which do not hesitate to eat certain soft
animals or animal products when they get the chance. Thus, both
monkeys and primitive men will eat grubs and small soft animals, and
also the eggs of birds. Whilst the cat tribe, in regard to the
chemical action of their digestive juices, are so specialised for
eating raw meat that it is practically impossible for them to take
vegetable matter as even a small portion of their diet, and whilst, on
the other hand, the grass-eating cattle, sheep, goats, antelopes, deer
and giraffes are similarly disqualified from any form of meat-diet,
most other land-mammals can be induced, without harm to themselves, to
take a mixed diet, even in those cases where they do not naturally
seek it. Pigs, on the one hand, and bears, on the other, tend
naturally to a mixed diet. Many birds, under conditions adverse to the
finding of their usual food, will change from vegetable to animal
diet, or _vice-versa_. Sea-gulls normally are fish-eaters, but some
will eat biscuit and grain when fish cannot be had. Pigeons have been
fed successfully on a meat diet; so, too, some parrots, and also the
familiar barn-door fowl. Many of our smaller birds eat both insects
and grain, according to opportunity. Hence it appears impossible to
base any argument against the use of cooked meat as part of man's diet
upon the structure of his teeth, or upon any far-reaching law of
Nature which decrees that every animal is absolutely either fitted
(internally and chemically, as well as in the matter of teeth) for a
diet consisting exclusively of vegetable substances, or else is
immutably assigned to one consisting exclusively of animal substances.
There is no _a priori_ assumption possible against the use as food by
man of nutritious matter derived from animals' bodies properly
prepared.
So far as _a priori_ argument has any value in such a matter, it
suggests that the most perfect food for any animal--that which
supplies exactly the constituents needed by the animal in exactly
right quantity and smallest bulk--is the flesh and blood of another
animal of its own species. This is a startling theoretical
justification--from the purely dietetic point of view--of
cannibalism. It is, however, of no conclusive value; the only method
which can give us conclusions of any real value in this and similarly
complex matters is prolonged, full, well-devised, well-recorded
experiment. At the same time, we may just note that the favourite food
of the scorpion is the juice of the body of another scorpion, and that
the same preference for cannibalism exists in spiders, many insects,
fishes, and even higher animals.
Another line of argument by which some advocates of vegetarianism
appeal to the popular judgment is by representing flesh-food derived
from animals as something dirty, foul, and revolting, full of microbic
germs, whilst vegetable products are extolled as being clean and
sweet--free from odour and putrescence and from the scaremonger's
microbes. This, I perhaps need hardly say, is a gigantic illusion and
misrepresentation. I came across it the other day in a very
unreasonable pamphlet on food by the American writer, Mr. Upton
Sinclair. Putrefactive microbes attack vegetable foods and produce
revolting smells and poisons in them, just as they do in foods of
animal origin. It is true that on the whole more varieties of
vegetable food can be kept dry and ready for use by softening with hot
water than is the case with foods prepared from animals. This is only
a question of not keeping food too long or in conditions tending to
the access of putrefactive bacteria. It is, on the whole, more usual
and necessary, in order to render it palatable, to apply heat to
flesh, fish, and fowl than to fruits. And it is by heat--heat of the
temperature of boiling water--applied for ten minutes or more, that
poison-producing and infective bacteria are killed and rendered
harmless. More people have become infected by deadly parasites and
have died from cholera and similar diseases, through having taken the
germs of those diseases into their stomachs with raw and over-ripe
fruit or uncooked vegetables and the manured products of the kitchen
garden, than have suffered from the presence of disease-germs or
putrefactive bacteria in well-cooked meat. Here, in fact, "cooking"
makes all the difference, just as it does in the matter we were
discussing above of the fitness of flesh and bone for trituration by
man's teeth.
[Illustration: Plate VI.--The series of teeth in the upper (1) and
lower jaw (2) of a modern European (natural size). The teeth are
placed closely side by side without a gap--an arrangement which does
not occur in the apes nor in any other living mammal, although it is
found in some extinct herbivores--the Anoplotherium and the
Arsinoeitherium. The shape of the arch formed by the row of teeth
should be compared with that shown by the same arch in the Gibbon (Pl.
VII). The crowns of the teeth are very carefully drawn in this figure,
which is from a plate published by Professor Selenka.
It must be noted that the number of tubercles on the true molars may
be in exceptional cases one more or one less than that given in this
drawing which gives the most usual number. The word "molar" is often
used to include the five cheek-teeth on each side of each jaw, but
more strictly the anterior bicuspid teeth are called "pre-molars," and
the three larger teeth behind them, which have no predecessors or
representatives in the first or milk dentition, are called true molars
or simply "molars"--a rule we have followed here.
In both upper and lower jaw we see the four incisors in the middle
(Inc. 1, Inc. 2); on each side of them is the conical crown of a
canine--a tooth which is greatly enlarged in the ape (see Pl. VII),
but is no larger proportionately than it is here even in the most
ancient known human jaw, that from the Pleistocene of Heidelberg (see
"Science from an Easy Chair," Methuen, 1910, p. 405). The two small
bicuspid "pre-molars" and the three large molars follow these on each
side in each jaw. The crown of the most anterior (or "first") molar of
the upper jaw has four cusps, tubercles, or cones on it. It is
"quadri-tuberculate." The second and third molars of the upper jaw
have three such prominent tubercles (excluding a row of small
tubercles on the hinder margin of the second); they are, in fact,
tri-tuberculate; whilst the two hindermost molars of the lower jaw
have four tubercles and are called quadri-tuberculate. The first molar
(M1) of the lower jaw has in this specimen five tubercles. In 60 per
cent. of European lower jaws this is the case. But in 40 per cent.
this tooth is quadri-tuberculate. In Polynesians, Chinese, Melanesians
and negroes five tubercles are found on this tooth in 90 per cent. of
the jaws examined. The apes are characterised by five tubercles on
this tooth, and they are found also on the first lower molars of
prehistoric men. Four tubercles only on this tooth is a departure from
the ape's condition and is found more frequently in Europeans.
It is obvious that these big molar teeth, as well as the two smaller
ones in front of them on each side of each jaw, are adapted for
breaking up rather soft, pulpy food, and not for cutting lumps of bone
or raw flesh, as are the molars of the clouded tiger (identical with
those of all species of the genus _Felis_), shown in Figs. 21 and 22,
pp. 103, 104, nor for rubbing grain, grass or herbage to a paste, as
are those of the goat (Fig. 17), those of the Coypu rat (Fig. 19), and
those of the elephants and mastodons (Fig. 8).]
[Illustration: Plate VII.--Drawings of (1) the upper and (2) the lower
series of teeth of the Gibbon (_Hylobates concolor_), one of the
anthropoid or most man-like apes (enlarged by one third). If these
drawings are compared with those in Pl. VI, showing man's teeth, the
most striking difference seen is that the "arch" or series of teeth is
here elongated and squared, not rounded in front, whilst there is
plenty of room in both jaws for the last or wisdom tooth, which is not
the case in modern races of men, though in the ancient Neander man's
jaw and in that from Heidelberg there is ample space for the last
molar as in the apes. The next most important difference is that in
the gibbon the four canine teeth are very large and tusk-like, and
must certainly be of value as weapons of attack--which man's are not.
Connected with the large size of the canines is the presence of a gap
(or "diastema" as it is called) between the four front teeth or
incisors of the upper jaw and the upper canine--which allows the lower
canine to fit in front of the upper canine when the jaw is closed. The
number of the tubercles or cones on the molars (the two smaller
pre-molars and the three hinder large molars) can be compared in
detail in these beautiful drawings from Professor Selenka's work,
which are the most careful and perfect which have ever been published.
The agreement of these teeth in man and the gibbon is very close: but
there are differences. The first, or most anterior pre-molar of the
lower jaw has one predominant cusp or cone; the second, like both in
the upper jaw, is "bicuspid," or bi-tuberculate, as in man. The three
big molars of the upper jaw are closely similar to those of man, with
some small differences, the second being quadri-tuberculate, whilst in
man it is as often tri-tuberculate (as it is in Pl. VI) as it is
quadri-tuberculate. But the two anterior big molars of the lower jaw
are seen to have each five well-marked cones, cusps or tubercles; they
are quinqui-tuberculate, whilst in man the first lower molar is often
quadri-tuberculate and the second even more frequently so. The last
lower molar (wisdom tooth) of the gibbon is like that of man,
quadri-tuberculate.
The details of the tubercles on these molar teeth distinctly justify
the conclusion that they are adapted in the two animals
compared--namely, man and the gibbon--to food of the same mechanical
quality, and this undoubtedly is fruit and nuts. Nevertheless such a
form of tooth is equally well adapted to the texture of cooked meat,
which has served many races of man for probably hundreds of thousands
of years as food.]
Once we remember that man is not fitted for the "raw meat" diet of the
carnivora, but is fitted for the "cooked meat" diet which he has
himself discovered--alone of all animals--we shall get rid of a
misleading prejudice in the consideration of the question as to
whether civilised men should or should not make cooked meat a portion
of their diet, with the purpose of maintaining themselves in as
healthy and vigorous a state as possible. Do not let us forget that
ancient Palaeolithic cave-men certainly made use of fire to cook their
meals of animal flesh, and that probably this use of fire dates back
to a still earlier period when, in consequence of this application of
the red, running tongues of flame, which he had learned to produce,
primitive man was able to leave the warmer climates of the earth and
their abundant fruits, and to establish himself in temperate and even
sub-Arctic regions.
Experiments on a large and decisive scale in regard to the value of
the different foods taken by man and the question of the desirability
of cooked meat as part of his diet have never been carried out, nor
has the use of alcohol been studied by direct experimental method on a
large scale. Inasmuch as the feeding of our Army and Navy, of
prisoners, lunatics, and paupers, is the business of the State, it is
obviously the duty of the Government to investigate this matter and
arrive at a decision. It can be done by the Government, and only by
the Government. The Army Medical Department is fully capable, and, I
am told, desirous, of undertaking this investigation. Five hundred
soldiers in barracks would find it no hardship, but an agreeable duty
(if rewarded in a suitable way), to submit to various diets, and to
comparative tests of the value of such diets. There would be no
difficulty in arranging the experimental investigation. Fifty years
ago similar work (but not precisely in regard to the questions now
raised) was done by the Army Medical Department, under Parkes, with
most valuable and widely recognised results.