some assistance in dealing with our difficult problem. It is commonly
assumed that the man-like apes are the most advanced members of the
Simian family save man alone, and so far as their present condition is
concerned this may be true. But it is not necessarily the case that
the anthropoid apes have advanced to their present condition. Judging
from the appearance of the young of these races, we may infer with some
degree of probability that these apes are the degraded representatives
of more intelligent and less savage creatures. Whereas the young of
man is decidedly more savage in character than the well-nurtured and
carefully trained adult, the young of apes are decidedly less savage
than the adult. The same reasoning which leads us to regard the
wildness, the natural cruelty, the destructiveness, the love of noise,
and many other little ways of young children, as reminders of a more or
less remote savage ancestry, should lead us to regard the comparative
tameness and quiet of the young gorilla, for example, as evidence that
in remote times the progenitors of the race were not so wild and fierce
as the present race of gorillas.
But even when all such considerations, whether based on the known or
the possible, have been taken into account, the gap between the lowest
savage and the highest ape is not easily bridged. It is easier to see
how man _may_ have developed from an arboreal, unspeaking animal to his
present state, than to ascertain how any part of the development was
actually effected; in other words, it is easier to suggest a general
hypothesis than to establish an even partial theory.
That the progenitor of man was arboreal in his habits seems altogether
probable. Darwin recognizes in the arrangement of the hair on the human
forearm the strongest evidence on this point, so far as the actual
body of man is concerned; the remaining and perhaps stronger evidence
being derived from appearances recognized in the unborn child. He,
who usually seems as though he could overlook nothing, seems to me to
have overlooked a peculiarity which is even more strikingly suggestive
of original arboreal habits. There is one set of muscles, and, so far
as I know, one only, which the infant uses freely, while the adult
scarcely uses them at all. I mean the muscles which separate the toes,
and those, especially, which work the big toe. Very young children
not only move the toes apart, so that the great toe and the little toe
will be inclined to each other (in the plane of the sole) nearly ninety
degrees, but also distinctly clutch with the toes. The habit has no
relation to the child’s actual means of satisfying its wants. I have
often thought that the child’s manner of clutching with its fingers is
indicative of the former arboreal habits of the race, but it is not
difficult to explain the action otherwise. The clutching movement of
the toes, however, cannot be so explained. The child can neither bring
food to its mouth in this way nor save itself from falling; and as the
adult does not use the toes in this way the habit cannot be regarded
as the first imperfect effort towards movements subsequently useful.
In fact, the very circumstance that the movement is gradually disused
shows that it is useless to the human child in the present condition
of the race. In the very young gorilla the clutching motion of the
toes is scarcely more marked than it is in a very young child; only in
the gorilla the movement, being of use, is continued by the young, and
is developed into that effective clutch with the feet which has been
already described. Here we have another illustration of that divergency
which, rather than either simple descent or ascent, characterizes the
relationship between man and the anthropoid ape. In the growing gorilla
a habit is more and more freely used, which is more and more completely
given up by the child as he progresses towards maturity.
Probably the arboreal progenitor of man was originally compelled to
abandon his arboreal habits by some slow change in the flora of his
habitat, resulting in the diminution and eventual disappearance of
trees suited for his movements. He would thus be compelled to adopt, at
first, some such course as the chimpanzee—making huts of such branches
and foliage as he could conveniently use for the purpose. The habit
of living in large companies would (as in the case of the chimpanzee)
become before long necessary, especially if the race or races thus
driven from their former abode in the trees were, like the gibbons,
unapt when alone both in attack and in defence. One can imagine how
the use of vocal signals of various kinds would be of service to the
members of these troops, not only in their excursions, but during the
work of erecting huts or defences against their enemies. If in two
generations the silent wild dog acquires, when brought into the company
of domestic dogs, no less than five distinct barking signals, we can
well believe that a race much superior in intelligence, and forced
by necessity to associate in large bodies, would—in many hundreds
of generations, perhaps—acquire a great number of vocal symbols.
These at first would express various emotions, as of affection, fear,
anxiety, sympathy, and so forth. Other signals would be used to
indicate the approach of enemies, or as battle-cries. I can see no
reason why gradually the use of particular vocal signs to indicate
various objects, animate or inanimate, and various actions, should
not follow after a while. And though the possession and use of many,
even of many hundreds, of such signs would be very far from even the
most imperfect of the languages now employed by savage races, one can
perceive the possibility—which is all that at present we can expect
to recognize—that out of such systems of vocal signalling a form of
language might arise, which, undergoing slow and gradual development,
should, in the course of many generations, approach in character
the language of the lowest savage races. That from such a beginning
language should attain its higher and highest developments is not more
wonderful in kind, though much more wonderful, perhaps, in degree,
than that from the first imperfect methods of printing should have
arisen the highest known developments of the typographic art. The
real difficulty lies in conceiving how mere vocal signalling became
developed into what can properly be regarded as spoken language.
Of the difficulties related to the origin of, or rather the development
of, man’s moral consciousness, space will not permit me to speak, even
though there were much to be said beyond the admission that these
difficulties have not as yet been overcome. It must be remembered,
however, that races of men still exist whose moral consciousness can
hardly be regarded as very fully developed. Not only so, but, through
a form of reversion to savage types, the highest and most cultivated
races of man bring forth from time to time (as our police reports too
plainly testify) beings utterly savage, brutal, and even (“which is
else”) bestial. Nay, the man is fortunate who has never had occasion
to control innate tendencies to evil which are at least strongly
significant of the origin of our race. To most minds it must be
pleasanter as certainly it seems more reasonable, to believe that the
evil tendencies of our race are manifestations of qualities undergoing
gradual extinction, than to regard them as the consequences of one
past offence, and so to have no reason for trusting in their gradual
eradication hereafter. But, as Darwin says, in the true scientific
spirit, “We are not here concerned with hopes or fears, only with
the truth as far as our reason allows us to discover it. We must
acknowledge that man, with all his noble qualities, with sympathy which
feels for the most debased, with benevolence which extends not only
to other men but to the humblest living creature, with his God-like
intellect which has penetrated into the movements and constitution of
the solar system,—with all these exalted powers, man still bears in
his bodily frame the indelible stamp of his lowly origin.” As it seems
to me, man’s moral nature teaches the same lesson with equal, if not
greater, significance.
_THE USE AND ABUSE OF FOOD._
Francis Bacon has laid it down as an axiom that experiment is the
foundation of all real progress in knowledge. “Man,” he said, “as the
minister and interpreter of nature, does and understands as much as
his observations on the order of nature permit him, and neither knows
nor is capable of more.”[41] It would seem, then, as if there could be
no subject on which man should be better informed than on the value
of various articles of food, and the quantity in which each should
be used. On most branches of experimental inquiry, a few men in each
age—perhaps but for a few ages in succession—have pursued for a
longer or shorter portion of their life, a system of experiment and
observation. But on the subject of food or diet all men in all ages
have been practical experimenters, and not for a few years only, but
during their entire life. One would expect, then, that no questions
could be more decisively settled than those which relate to the use or
the abuse of food. Every one ought to know, it might be supposed, what
kinds of food are good for the health, in what quantity each should
be taken, what changes of diet tend to correct this or that kind of
ill-health, and how long each change should be continued.
Unfortunately, as we know, this is far from being the case. We all
eat many things which are bad for us, and omit to eat many things
which would be good for us. We change our diet, too often, without
any consideration, or from false considerations, of the wants of the
body. When we have derived benefit from some change of diet, we are apt
to continue the new diet after the necessity for it has passed away.
As to quantity, also, we seldom follow well-judged rules. Some take
less nutriment (or less of some particular form of nutriment) than
is needed to supply the absolute requirements of the system; others
persistently overload the system, despite all the warnings which their
own experience and that of others should afford of the mischief likely
to follow that course.
It is only of late years that systematic efforts have been made to
throw light on the subject of the proper use of food, to distinguish
between its various forms, and to analyze the special office of each
form. I propose to exhibit, in a popular manner, some of the more
important practical conclusions to which men of science have been led
by their investigations into these questions.
The human body has been compared to a lamp in which a flame is burning.
In some respects the comparison is a most apt one, as we shall see
presently. But man does more than _live_; he _works_,—with his
brain or with his muscles. And therefore the human frame may be more
justly compared to a steam-engine than to the flame of a lamp. Of
mere life, the latter illustration is sufficiently apt, but it leaves
unillustrated man’s capacity for work; and since food is taken with
two principal objects—the maintenance of life and the renewal of
material used up in brain work and muscular work—we shall find that
the comparison of man to a machine affords a far better illustration
of our subject than the more common comparisons of the life of man
to a burning flame, and of food to the fuel which serves to maintain
combustion.
There is, however, one class of food, and, perhaps, on the whole, the
most important, the operation of which is equally well illustrated by
either comparison. The sort of food to which I refer may be termed
_heat-maintaining_ food. I distinguish it thus from food which serves
other ends, but of course it is not to be understood that any article
of diet serves _solely_ the end of maintaining heat. Accordingly, we
find that heat-maintaining substance exists in nearly all the ordinary
articles of food. Of these there are two—sugar and fat—which may be
looked on as special “heat-givers.” Starch, also, which appears in all
vegetables, and thus comes to form a large proportion of our daily
food, is a heat-giver. In fact, this substance only enters the system
in the form of sugar, the saliva having the power of converting starch
(which is insoluble in water) into sugar, and thus rendering it soluble
and digestible.
Starch, as I have said, appears in all vegetables. But it is found
more freely in some than in others. It constitutes nearly the whole
substance of arrowroot, sago, and tapioca, and appears more or less
freely in potatoes, rice, wheat, barley, and oats. In the process
of vegetation it is converted into sugar; and thus it happens that
vegetable diet—whether presenting starch in its natural form to
be converted into sugar by the consumer, or containing sugar which
has resulted from a process of change undergone by starch—is in
general heat-maintaining. Sugar is used as a convenient means of
maintaining the heat-supply; for in eating sugar we are saved the
trouble of converting starch into sugar. A love for sweet things is
the instinctive expression of the necessity for heat-maintaining
food. We see this liking strongly developed in children, whose rapid
growth is continually drawing upon their heat-supply. So far as adults
are concerned, the taste for sweet food is found to prevail more in
temperate than in tropical climes, as might be expected; but, contrary
to what we might at first expect, we do not find any increase in
the liking for sweet food in very cold climates. Another and a more
effective way of securing the required heat-supply prevails in such
countries.
As starch is converted into sugar, so by a further process sugar is
converted into fat. It is by the conversion of sugar into fat that
its heat-supplying power is made available. This conversion takes
place in the vegetable as well as in the animal system, and thus fat
appears in a variety of forms—as butter, suet, oil, and so forth. Now,
precisely as sugar is a more convenient heat-supplier than starch,
so fat exceeds sugar in its power of maintaining animal heat. It has
been calculated that one pound of fat—whether in the form of suet,
butter, or oil—will go as far towards the maintenance of animal heat
as two pounds of sugar, or as two pounds and a half of starch. Thus
it happens that in very cold countries there is developed a taste for
such articles of food as contain most fat, or even for pure fat and its
analogues—oil, butter, tallow, dripping, and other forms of _grease_.
I have spoken of starch, sugar, and fat as heat-forming articles of
food; but I must note their influence in the development of muscles and
nerves. Without a certain proportion of fat in the food a wasting of
the tissues will always take place; for muscles and nerves cannot form
without fat. And conversely, the best remedy for wasting diseases is to
be found in the supply of some easily digestible form of fatty food.
Well-fatted meat, and especially meat in which the fat is to be seen
distributed through the flesh, may be taken under such circumstances.
Butter and salad oil are then also proper articles of food. Cream is
still better, and cream cheeses may be used with advantage. It is on
account of its heat-supplying and fat-forming qualities that cod-liver
oil has taken its place as one of the most valuable remedies for
scrofulous and consumptive patients.
But it must be noted that the formation of fat is not the object with
which heat-supplying food is taken. It is an indication of derangement
of the system when heat-giving food is too readily converted into
fat. And in so far as this process of conversion takes place beyond
what is required for the formation of muscles and nerves, the body
suffers in the loss of its just proportion of heat-supply. Of course,
if too large an amount of heat-giving food is taken into the system,
we may expect that the surplus will be deposited in the form of
adipose tissue. The deposition of fat in such a case will be far less
injurious to the system than an excessive heat-supply would be. But
when only a just amount of heat-giving food is taken, and in place
of fulfilling its just office this food is converted into adipose
tissue, it becomes necessary to inquire into the cause of the mischief.
Technically, the evil may be described as resulting from the deficient
oxygenation of the heat-supplying food. This generally arises from
defective circulation, and may often be cured by a very moderate but
_systematic_ increase in the amount of daily exercise, or by the use
of the sponge-bath, or, lastly, by such changes in the dress—and
especially in the articles of attire worn next to the skin—as tend to
encourage a freer circulation of the blood. The tendency to accumulate
fat may sometimes be traced to the use of over-warm coverings at night,
and especially to the use of woollen night-clothes. By attending to
considerations of this sort, more readily and safely than by an undue
diminution of the amount of heat-supplying food, the tendency to
obesity may frequently be corrected.
In warm weather we should diminish the supply of heat-giving food. In
such weather the system does not require the same daily addition to its
animal heat, and the excess is converted into fat. Experiments have
shown that despite the increased rate at which perspiration proceeds
during the summer months, men uniformly fed throughout the year
increase in weight in summer and lose weight in winter.
So far as mere existence is concerned, heat-forming food may be looked
upon as the real fuel on which the lamp of life is sustained. But man,
considered as a working being, cannot exist without _energy-forming_
food. All work, whether of the brain or of the limbs, involves the
exhaustion of nervous and muscular matter; and unless the exhausted
matter be renewed, the work must come to an end. The supply of
heat-giving food may be compared to the supply of fuel for the fire
of a steam-engine. By means of this supply the _fire_ is kept alive;
but if the fire have nothing to work upon, its energies are wasted or
used to the injury of the machine itself. The supply of water, and its
continual use (in the form of steam) in the propulsion of the engine,
are the processes corresponding to the continual exhaustion and renewal
of the muscles and nerves of the human frame. And the comparison may be
carried yet further. We see that in the case of the engine the amount
of smoke, or rather of carbonic acid, thrown out by the blast-pipe is
a measure of the vital energy (so to speak) within the engine; but the
amount of work done by the engine is measured rather by the quantity of
steam which is thrown out, because the elastic force of every particle
of steam has been exerted in the propulsion of the engine before being
thrown out through the blast-pipe. In a manner precisely corresponding
to this, the amount of carbonic acid gas exhaled by a man is a measure
of the rate at which mere existence is proceeding; but the amount of
work, mental or muscular, which the man achieves, is measured by the
amount of used-up brain-material and muscle-material which is daily
thrown off by the body. I shall presently show in what way this amount
is estimated.
In the composition of the muscles there is a material called _fibrine_,
and in the composition of the nerves there is a material called
_albumen_. These are the substances[42] which are exhausted during
mental and bodily labour, and which have to be renewed if we are to
continue working with our head or with our hands. Nay more, life itself
involves work; the heart, the lungs, the liver, each internal organ of
the body, performs its share of work, just as a certain proportion of
the power of a steam-engine is expended in merely moving the machinery
which sets it in action. If the waste of material involved in this form
of work is not compensated by a continual and sufficient supply of
fibrine and albumen the result will be a gradual lowering of all the
powers of the system, until some one or other gives way,—the heart
ceases to beat, or the stomach to digest, or the liver to secrete
bile,—and so death ensues.
The fibrine and albumen in the animal frame are derived exclusively
from vegetables. For although we seem to derive a portion of the
supply from animal food, yet the fibrine and albumen thus supplied
have been derived in the beginning from the vegetable kingdom. “It is
the peculiar property of the plant,” says Dr. Lankester, “to be able,
in the minute cells of which it is composed, to convert the carbonic
acid and ammonia which it gets from the atmosphere into fibrine
and albumen, and by easy chemical processes we can separate these
substances from our vegetable food. Wheat, barley, oats, rye, rice, all
contain fibrine, and some of them also albumen. Potatoes, cabbage, and
asparagus contain albumen. It is a well-ascertained fact that those
substances which contain most of these ‘nutritious secretions,’ as they
have been called, support life the longest.” They change little during
the process of digestion, entering the blood in a pure state, and being
directly employed to renew the nervous and muscular matter which has
been used up during work, either mental or muscular. Thus the supply
of these substances is continually being drawn upon. The carbon, which
forms their principal constituent, is converted into carbonic acid;
and the nitrogen, which forms about a sixth part of their substance,
re-appears in the nitrogen of urea, a substance which forms the
principal solid constituent of the matter daily thrown from the system
through the action of the kidneys. Thus the amount of urea which daily
passes from the body affords a measure of the work done during the day.
“This is not,” says Dr. Lankester, “the mere dream of the theorist;
it has been practically demonstrated that increased stress upon the
nervous system, viz., brain work, emotion, or excitement from disease,
increases the quantity of urea and the demand for nitrogenous food. In
the same manner the amount of urea is the representative of the amount
of muscular work done.”
It has been calculated that the average amount of urea daily formed
in the body of a healthy man is about 470 grains. To supply this
daily consumption of nitrogenous matter, it is necessary that about
four ounces of flesh-forming substance should be consumed daily.
It is important, therefore, to inquire how this substance may be
obtained. The requisite quantity of albuminous and fibrinous matter
“is contained,” says Dr. Lankester, “in a pound of beef; in two pounds
of eggs; in two quarts of milk; in a pound of peas; in five pounds of
rice; in sixteen pounds of potatoes; in two pounds of Indian meal;
in a pound and a half of oatmeal; and in a pound and three-quarters
of flour.” A consideration of this list will show the importance of
attending to the quality as well as the quantity of our food. A man
of ordinary appetite might satisfy his hunger on potatoes or on rice,
without by any means supplying his system with a sufficient amount of
flesh-forming food. On the other hand, if a man were to live on bread
and beef alone, he would load his system with an amount of nitrogenous
food, although not taking what could be considered an excessive amount
of daily nourishment. We see, also, how it is possible to continually
vary the form in which we take the required supply of nitrogenous food,
without varying the amount of that supply from day to day.