intellectual activity, it seems not unnatural to assume for man, as the
rational animal, a very distinctive cerebral development. One of the
most distinguished of living naturalists, Professor Owen, has even made
this organ the basis of a system of classification, by means of which he
separates man into a sub-class, distinct from all other mammalia. But
while a comparison between man and the anthropoid apes, as the animals
most nearly approximating to him in physical structure, lends
confirmation to the idea not only that a well-developed brain is
essential to natural activity, but that there is a close relation
between the development of the brain and the manifestation of
intellectual power; the distinctive features in the human brain, as
compared with those of the anthropomorpha, prove to be greatly less than
had been assumed under imperfect knowledge. The substantial difference
is in volume. “No one, I presume,” says Darwin, “doubts that the large
size of the brain in man, relatively to his body, in comparison to that
of the gorilla or orang, is closely connected with his higher mental
powers”;[152] and it might not unfairly be reasoned from analogy, that
the same test distinguishes the intellectual man from the stolid, and
the civilised man from the savage. A careful study of the subject,
however, shows some remarkable deviations from such a scale of
progression. Attention is indeed directed to greatly more ample proofs
of inequality between the organic source of power and the manifestations
of mental energy; as, for example, in the ant, with its cerebral ganglia
not so large as the quarter of a small pin’s head, displaying instincts
and apparent affections of wonderful intensity and compass. Viewed in
this aspect, “the brain of an ant is one of the most marvellous atoms of
matter in the world, perhaps more marvellous than the brain of man.”
Here, however, we look on elements of contrast rather than analogy; and
seek in vain in this direction for any appreciable test of the soundness
of the popular belief in the size of the brain as a measure of
intellectual power. It is otherwise when we turn to the anthropomorpha.
There, alike in the scientific and in the popular creed, very special
and exceptional affinities to man are admitted; and a careful study of
their anatomical structure tends to increase the recognised points of
analogy.
Mr. Lockhart Clarke, in a contribution to Dr. Maudsley’s work on the
Physiology and Pathology of Mind, gives a minute description of the
concentric layers of nervous substance which combine to form the
convolutions of the human brain; and of the forms and disposition of the
various nerve-cells of which its vesicular structure consists. Comparing
the human brain with those of other animals, he says: “Between the cells
of the convolutions in man and those of the ape tribe I could not
perceive any difference whatever; but they certainly differ in some
respects from those of the larger mammalia: from those, for instance, of
the ox, sheep, or cat.”[153] Apart from the difference in volume (55 to
115 cubic inches), the only distinctive features, according to Professor
Huxley, between the brain of the anthropomorpha and that of man, are
“the filling up of the occipito-temporal fissure; the greater complexity
and less symmetry of the other sulci and gyri; the less excavation of
the orbital face of the frontal lobe; and the larger size of the
cerebral hemispheres, as compared with the cerebellum and the cerebral
nerves.”
The brain of the orang is the one which seems most nearly to approximate
to that of man. In volume it is about 26 or 27 cubic inches; or about
half the minimum size of a normal human brain. The frontal height is
greater than in that of other anthropomorpha; the frontal lobe is in all
respects larger as compared with the occipital lobe; and certain folds
of brain-substance, styled “bridging convulsions,” which in the human
brain are interposed between the parietal and occipital lobes, also
occur, though greatly reduced, in the brain of the orang; while they
appear to be wholly wanting in the chimpanzee, the gibbon, and other
apes which superficially present a greater resemblance to man. Referring
to the convolutions of the central cerebral lobe, Huschke says: “With
their formation in the ape, the brain enters the last stage of
development until it arrives at its perfection in man”; and the higher
class of brains may be arranged between the extremes of poorly and
richly convoluted examples.
But it must not be overlooked that, apart from structural differences,
relative, and not absolute mass and weight of brain has to be
considered, otherwise the elephant and the whale would take the foremost
place. “The brain of the porpoise,” Professor Huxley remarks,[154] “is
quite wonderful for its mass, and for the development of the cerebral
convolutions”; but it is the centre of a nervous system of corresponding
capacity, while as compared with the size of the animal, the brain is
not relatively large. Vogt states the weight of the human body to be to
the brain, on an average, as 36 to 1; whereas in the most intelligent
animals the difference is rarely less than 100 to 1.
Assuming the existence of some uniform relation between the size of the
brain and the development of the intellectual faculties, along with
whatever is recognised as most closely analogous to them in the lower
animals, it might be anticipated that we should find not only a
graduated development of brain in the anthropomorpha as they approximate
in resemblance to man; but, still more, that the progressive stages from
the lowest savage condition to that of the most civilised nations should
be traceable in a comparative size and weight of brain. Dr. Carl Vogt,
after discussing certain minor and doubtful exceptions, thus proceeds:
“We find that there is an almost regular series in the cranial capacity
of such nations and races as, since historic times, have taken no part
in civilisation. Australians, Hottentots, and Polynesians, nations in
the lowest state of barbarism, commence the series; and no one can deny
that the place they occupy in relation to cranial capacity and cerebral
weight corresponds with the degree of their intellectual capacity and
civilisation.”[155] But the position thus confidently assigned to the
Polynesians receives no confirmation from the evidence supplied by the
measurements of Dr. J. B. Davis, in his _Thesaurus Craniorum_; and a
careful study of the subject reveals other remarkable deviations from
such a scale of progression, not only in individuals but in races. To
these exceptional deviations, with their bearing on the comparative
capacity of races, the following remarks are chiefly directed. The
largest and heaviest brains do indeed appear, for the most part, to
pertain to the nations highest in civilisation, and to the most
intelligent of their number. But this cannot be asserted as a uniform
law, either in relation to races or individuals. The more carefully the
requisite evidence is accumulated, the less does it appear that the
volume of brain, or the cubic contents of the skull, supply a uniform
gauge of intellectual capacity. In the researches which have thus far
been instituted into the characteristics of the human brain among the
lowest races, the development is in many respects remarkable; and, as
was to be expected, no organic differences between diverse races of men
have been traced.
Professor C. Luigi Calori has published the results of a careful
examination of the brain of a negro of Guinea. It presented the marked
excess of length over breadth so characteristic of the negro cranium;
but in other respects it corresponded generally to the fully developed
European brain. The distribution of the white and gray substances was
the same; the cerebral convolutions were collected into an equal number
of lobes; and the only special difference was that the convolutions were
a little less frequently folded, and the separating sulci somewhat less
marked than in the average European brain. But even in those respects
the complication was great. The actual weight of the brain, according to
Professor Calori, was 1260 grammes, equivalent to 44.4 cubic inches. The
complexity of convolution, and consequent extension of superficies of
the encephalon, appears to be an essential element in the development of
the brain as the organ of highest mental capacity; and to the cerebrum,
apparently, the true functions of intellectual activity pertain.
Professor Wagner undertook the measurement of the convex surface of the
frontal lobe in a series of brains. The heaviest, as a rule, had also
the greatest development of surface. But the two elements were not in
uniform ratio. Some of the lighter brains presented a much greater
degree of convolution and consequent extent of convex superficies than
others which ranked above them in weight. It is thus apparent that in
estimating the comparative characteristics of brains, various elements
are necessary for an exhaustive comparison. Besides the functional
differences of the cerebrum, cerebellum, and pons varolii, they have
different specific gravities, so that brains of equal weight may differ
widely in quality. Dr. Peacock, taking distilled water as 1000, gives
the values of the subdivisions of the brain thus: cerebrum, 1034;
cerebellum, 1041; pons varolii, 1040. Again, Dr. Sankey states the mean
specific gravity of the gray matter of the brain in either sex as
1034.6, and of the white matter as 1041.2. The variations from these
results, as given by Bastian, Thurnam, and others, are trifling. But it
is significant to note that recent researches show that where greater
specific gravity of brain occurs in the insane, it appears to be limited
to the gray matter.[156] Professor Goodsir maintained that symmetry of
brain has more to do with the higher faculties than bulk of form. It is,
at any rate, apparent that two brains of equal weight may differ widely
in quality.
Nevertheless, the popular estimate embodied in such expressions as “a
good head,” “a long-headed fellow,” and “a poor head,” like many other
popular inductions, has truth for its basis. Up to a certain stage the
growth of the brain determines the capacity of the skull. Then it seems
as though more complex convolutions accompanied the packing of the
elaborated cerebral mass within the fixed limits of its osseous chamber.
A comparison of races, based on minute investigation of an adequate
number of brains of fair typical examples, may be expected to yield
important results; but in the absence of such direct evidence, the chief
data available for this purpose are derived from measurements of the
internal capacity of their skulls. Among English observers who have
devoted themselves to this class of observations, the foremost place is
due to Dr. J. Barnard Davis, who, in 1867, summed up the results of his
extensive researches in a contribution to the Royal Society, entitled
“Contributions towards determining the Weight of the Brain in different
Races of Man.”[157] Inferior as such evidence must necessarily be, if
compared with the examination of the brain itself, nevertheless the
number of skulls of the different races gauged unquestionably furnishes
some highly valuable data for ethnical comparison. The evidence,
moreover, is obtained from a source in some respects less variable than
the encephalon; and will always constitute a corrective element in
estimating results based on direct examinations of the brain. Dr. Davis,
indeed, claims “that the examination of a large series of skulls in
ascertaining their capacities and deducing from those capacities the
average volume of the brain, affords in some respects more available
data for determining this relative volume for any particular race than
the weighing of the brain itself.” The defect is, that its most
important results are necessarily based on the assumption of a uniform
density of brain; whereas some notable ethnical differences, hereafter
referred to, may prove to be due to the fact that certain races derive
their special characteristics from a prevailing diversity in this very
respect.
But the extensive observations of Dr. Davis, as of Dr. Morton, have a
special value from the fact that each furnishes results based on a
uniform system of observation; for the diverse methods and materials
employed by different observers in gauging the human skull have greatly
detracted from their practical value. In a communication by the late
Professor Jeffreys Wyman to the Boston Natural History Society,[158] he
presented the results of a series of measurements of the internal
capacity of the same skull with pease, beans, rice, flax-seed, shot, and
coarse and fine sand. From repeated experiments he arrived at the
conclusion that the apparent capacity varied according to the different
substances used, so that the same skull measured respectively, with
pease 1193 centimetres, with shot 1201.8, with rice 1220.2, and with
fine sand 1313 centimetres. Professor Wyman was led to the conclusion
that, for exactness, small shot, as employed latterly by Dr. Morton, is
preferable to sand, were it not for its weight, which, in the case of
old and fragile skulls, is apt to be destructive to them. With a view to
avoid the latter evil, Dr. J. B. Davis has used fine Calais sand of
1.425 specific gravity. The diversity in apparent volume, consequent on
the employment of different substances in gauging the internal capacity
of the skull, necessarily detracts from the value of comparative results
of Morton, Davis, and others. But the elaborate measurements of their
great collections of human crania furnish reliable series of data, each
uniform in system, and sufficiently minute to satisfy many requirements
of comparative craniometry and approximate cerebral development.
Without assuming an invariable correspondence in cubical capacity and
brain-weight, there is a sufficient approximation in the cubical
capacity of the skull and the average weight of the encephalon to render
the deductions derived from gauging the capacities of skulls of
different races an important addition to this department of comparative
ethnology. For minute cerebral comparisons, however, it is apparent that
much more is required; and the special functions assigned to the various
organs within the cranium have to be kept in view. Of these the medulla
oblongata, in direct contact with the spinal cord, is now recognised as
the centre of the vital actions in breathing and swallowing; and is
believed also to be the direct source of the muscular action employed in
speech. Next to it are the sensory ganglia, arranged in pairs along the
base of the brain. To the cerebellum, which the phrenologist sets apart
as the source of the emotions and passions embraced in his terminology
of amativeness, philoprogenitiveness, etc., physiologists now assign the
function of conveying to the mind the conditions of tension and
relaxation of the muscles, and so controlling their voluntary action.
But above all those is the cerebrum, or brain-proper, consisting of two
large lobes of nervous substance, which in man are so large that, when
viewed vertically, they cover and conceal the cerebellum. To this organ
is specially assigned emotion, volition, and ratiocination. It is the
assumed seat of the mind; and, in a truer sense than the skull—
The dome of thought, the palace of the soul;
if indeed it be not, to one class of reasoners, the mind itself. Certain
it is that no acute disease can affect it without a corresponding
disorder of the functions of mind; and with this organ much below the
average size, intellectual weakness may always be predicated. But at the
same time, it is significant to note that the human brain, stinted in
its full proportions, and reduced to a seeming equality with the
anthropomorpha, exhibits no corresponding capacities or instincts in
lieu of the higher mental qualities. Microcephaly is the invariable
index, not of mere limited intelligence and mental capacity, but of
actual mental imbecility. If the augmentation of the brain of the
anthropomorpha from 55 to 115 cubic inches be all that is requisite for
the transformation of the irrational ape into the reasoning man, it
would seem to be in no degree illogical to look for the accompaniment of
the inversion of the process by an approximation, in some instances, to
certain capacities and functions of the ape. But there are no
indications of this. In some examples of microcephaly, the so-called
animal propensities do indeed manifest themselves to excess; but there
is no reproduction of the animal nature, instincts, or capacities,
analogous to the scale of cerebral development of the orang or
chimpanzee. A microcephalous idiot, who died at the age of twenty-two,
in St. Bartholomew’s Hospital, London, had a brain weighing only 13.125
oz., or 372 grammes. In describing this case, Professor Owen remarks:
“Here nature may be said to have performed for us the experiment of
arresting the development of the brain almost exactly at the size which
it attains in the chimpanzee, and where the intellectual faculties were
scarcely more developed. Yet no anatomist would hesitate in at once
referring the cranium to the human species.” And so is it with the
encephalon. The brain of the chimpanzee is a healthy, well-developed
organ, adequate to the amplest requirements of the animal; whereas the
microcephalous human brain is inadequate for any efficient, continuous
cerebral activity: not merely limited in its range of powers. Much,
however, may yet be learned from a careful attention to the imperfect
manifestations of activity in certain directions, in cases of
microcephalic idiocy, and noting the predominant tendency in each case,
with a view to subsequent examination of the brain. By this means it may
be found possible to refer certain forms of mental activity to special
variations in the structure of the organ, or to distinct members of the
encephalon.
Dr. Laennec exhibited to the Anthropological Society of Paris a
microcephalous idiot of the male sex, aged fourteen years. “This child
is entirely unconscious of his own actions, and his intellectual
operations are very few in number, and very rudimentary. His language
consists of two syllables, _oui_ and _la_, and he takes an evident
pleasure in pronouncing them. He takes no heed in what direction he
walks. He would step off a precipice, or into a fire.” Attention was
specially directed to the idiot’s hands: “The thumbs are atrophied, and
cannot be opposed to the other fingers. The palms of the hands have the
transverse creases, but not the diagonal—the result of the atrophy of
the thumbs. Hence the hand resembles that of the chimpanzee. The
dentition too is defective. Though fourteen years of age, the child has
only twelve teeth.” Here it is curious to note the analogies in physical
structure to the lower anthropomorpha in other organs besides the brain,
for it only renders more striking the absence of any corresponding
aptitudes.
Dr. J. Barnard Davis, in his interesting monograph on _Synostotic Crania
among Aboriginal Races of Man_, produces some remarkable illustrations
of the effect of premature ossification of the sutures of the skull in
arresting the full development of the brain, and so rendering it unequal
to the due performance of its functions. “I have,” he says, “the cranium
of a convict who was executed on Norfolk Island, which I owe to the
kindness of Admiral H. M. Denham. This man was executed there when that
beautiful isle was appropriated to the reception of the most dangerous
and irreclaimable convicts from the other penal settlements. It is a
microcephalic skull, rather dolichocephalic, of a man apparently about
forty years of age. It exhibits a perfect ossification of the sagittal
and of the greater portion of the lambdoidal sutures. The coronal suture
is partially obliterated at the sides in the temporal regions, and can
only be distinguished by faint traces in all its middle parts. In this
case there has not been any compensatory development of moment in other
directions. The calvarium is not abridged in its length, which is 7.1
inches, equal to 179 millimetres; probably it is a little elongated. It
is, however, very narrow being only 4.8 inches, or 122 mm. at its widest
part, between the temporal bones. So that the result is a very small,
dwarfed, almost cylindrical calvarium. The internal capacity is only 59
ounces of sand,[159] which is equal to 71.4 cubic inches, or 1169 cubic
centimetres.” Here is a skull considerably below the lowest mean of the
crania of any race in Morton’s enlarged tables, or in the more
comprehensive ones furnished in Dr. Davis’s _Thesaurus Craniorum_.
Another skull nearly approximating to it is that of a Cole, one of the
savage tribes of Nagpore, in Central India, who are said to go entirely
naked. It is described in the supplement to the _Thesaurus Craniorum_ as
that of “Chara,” a Cole farmer, aged fifty, and its internal capacity is
stated as 59.5 oz. av., equivalent to 71.7 cubic inches. The Coles
appear to be small of stature. The heights of three of them, whose
skulls are in the same collection, were respectively 5 ft. 5 in., 5 ft.
2 in., and 5 ft., and the average internal capacity of five male skulls
is only 66.6. The small stature in this and others of the native races
of Central India, has to be taken into account in estimating the
relative size of the brain. But, after making all due allowance for
this, the Cole skulls are remarkable for their small size, being smaller
even than the ordinary Hindoos of Bengal. Yet one of them, “Cootlo,”
whose skull is among those included in the above mean, commanded a band
of insurgents in the Porahant rebellion of 1858, and made himself a
terror to the district.
The microcephalism of races, as well as of individuals, of small
stature, must not be confounded with the true microcephaly of a dwarfed
or imperfectly developed brain, which is invariably accompanied with
mental imbecility. The Mincopies of the Andaman Islands are spoken of by
Professor Owen as “perhaps the most primitive, or lowest in the scale of
civilisation, of the human race.”[160] Mr. G. E. Dobson, in describing
his first visit to one of their “homes,” says: “Although none of the
tribe exceeded 64 inches in height, so that on first seeing them we
thought the shed contained none but boys and girls, I was especially
struck by the remarkable contrast between the size of the males and
females.”[161] Dr. J. B. Davis has given, in the supplement to
_Thesaurus Craniorum_, the dimensions of a male Mincopie skeleton in his
collection. The age he assumes to have been about thirty-five. The
internal capacity of the skull is 62 oz. (Calais sand), equivalent to
75.5 cubic inches, and the entire height of the skeleton is 58.7 inches.
It belongs, says Dr. Davis, to a pigmy race, is small in all its
dimensions, and is particularly small in the dimensions of the pelvis.
Of their skulls, moreover, he adds, “it is somewhat difficult to
determine the sex with confidence. They are all small (but this is a
character of the race), they are delicate in development, and they have
that fulness of the occipital region, and smallness of the mastoid
processes, which are marks of femininism.”
Mr. Alfred R. Wallace connects the Mincopies with the Negritos and
Semangs of the Malay peninsula, a dark woolly-haired race, dwarfs in
stature. Dr. Davis says of the six Mincopie skulls in his collection,
four male and two female, as well as of others which he has seen: “They
are all remarkably and strikingly alike, not merely in size but in form
also. They are all small, round, brachycephalic crania of beautiful
form.” Moreover, though classed as “lowest in the scale of
civilisation,” the Mincopies betray no deficiency of intellect. The
admirable photographs which illustrate Mr. Dobson’s narrative show in
the majority of them good frontal development. The brain is not, indeed,
relatively small. Their canoes are made of the trunk of a tree, hollowed
out; and Mr. Dobson remarks: “The construction of their peculiar arrows
and fish-spears with movable heads exhibits much ingenuity, and the use
of no small reasoning power in adapting means to an end.”