and general uniformity in tbe size of tide grains. But it was soon
manifest that the utmost care could not prevent considerable variation
in several successive measurements, sometimes amounting to three
or four cubic inches. Under these circumstances, hut not until all
the internal capacity measurements of the Crania Americana had been
made in this way, I saw the necessity of devising some other medium
with which to fill the cranium; and after a fall trial of the shot, have
permanently adopted it, with the satisfactory results above stated.*
These remarks will explain the difference between the measurements
published in the Crania Americana and those obtained from the same
skulls by the revised method.f
In an investigation of this nature, the question arises — At what
age does the brain attain, full development ? On this point, there is
great diversity of opinion. Professor Sommering supposes this period
to he as early as the third year. Sir William Hamilton expresses
himself in the following terms: “ In man, the encephalon reaches its
full size about seven years of age. This,” he adds, “ was never before
proved.” The latter remark leads us to infer that this able and laborious
investigator regarded his proposition as an incontestable fact.
Professor Tiedemann assumes the eighth year as the period of the
brain’s maximum growth.
Dr. Sims, on the other hand, inferred from an extended series of
experiments on the brain from a year old to upwards of seventy,
that “ the average weight goes on increasing from one year to twenty;
between twenty and thirty there is a slight increase in the average;
afterwards it increases, and arrives at the maximum between forty
and fifty. After fifty, to old age, the brain gradually decreases in
weight.” These observations nearly correspond with those of Dr.
Gall, but are liable to various objections.
Dr. John Reid has also investigated this question on a large scale
and with great care. After weighing 253 brains of both sexes and
of various ages, he arrives at the conclusion that the encephalon
arrives at its maximum size sooner than the other organs of the body;
that its relative size, when compared with the other organs, and to
the entire body, is much greater in the child than in the adult; and
that although the average weight of the male brain is absolutely
heavier than that of the female, yet the avfrage female brain, relative
to the whole body, is somewhat heavier than, the average male brain.
Finally, he observes that his experiments do not afford any support
to the proposition that the encephalon attains its maximum weight
at or near the age of seven years. On this latter point, which is of
* Proceedings of the Academy of Nat. Sciences of Philad. for April, 1841.
t See my Catalogue of Skulls, 3d ed. 1849.
great importance in the present inquiry, I shall offer a few remarks.
The most obvious use of the sutures of the cranium is to subserve
the process of growth, which they do by osseous depositions at their
margins. Hence one of these sutures is equivalent to the interrupted
structure that exists between the shaft and epiphysis of a long bone
in the growing state. The shaft grows in length chiefly by accretions
at its extremities; and the epiphysis, like the cranial suture, disappears
when the perfect development is accomplished. Hence we may
infer that the skull ceases to expand whenever the sutures become
consolidated with the proximate bones. In other words, the growth
of the brain, whether in viviparous or in oviparous animals, is. con- •
sentaneous with that of the skull, and neither can be developed without
the presence of free sutures.*
From these considerations, and from many comparisons, I cannot
admit that the brain has attained its physical maturity at the age of
seven, or eight years; neither is there satisfactory evidence to prove
that it. continues to grow after adult age. It may possibly increase
and decrease in size, and weight after that period, without altering
the internal capacity of the cranium, which last measurement will
always indicate the maximum size the encephalon had attained at
(the) period of its greatest development; for in those instances in
which this organ has been observed in a contracted or shrunken
state, in very old persons, the cranial cavity has remained to all appearance
unaltered, f
"We know that at, and often before, the age o | sixteen years the
sutures are already so firmly anchylosed as not to be separated without
great difficulty, or even without fracture; whence we may reasonably
infer that the encephalon has nearly, if not entirely, attained its
* I have in my possession the skull of a mulatto boy who died at the age of eighteen
years. In this instance, the sagittal suture is entirely wanting; in consequence, the lateral
expansion of the cranium has ceased in infancy, or at whatever period the suture became
consolidated. Hence also the diameter between the parietal protuberances is less than 4.5
inches, instead of 5, which last is the Negro average. The squamous sutures, however,
are fully open, whence the skull has continued to expand in the upward direction, until
it has reached the average vertical diameter of the Negro, or 5.5 inches. The coronal
suture is also wanting, excepting some traces at its lateral termini; and the result of this
last deficiency is seen in the very inadequate of the forehead, which is low and narrow,
but elongated below through the agency of the various cranio-facial sutures. The lamdoidal
suture is perfect, thus permitting posterior elongation; and the growth in this direction,
together with the full vertical diameter, has enabled the brain to attain the bulk o f ------
cubic inches or about less than the Negro average. I believe that the absence or
partial development of the sutures may be a cause of idiocy by checking the growth of the
brain, and thereby impairing or destroying its functions. See Proceedings of the Academy,
for August, 1841.
f Mr. George Combe, System of Phrenology, p. 83, is of the opinion that when the brain
contracts, the inner table of the skull follows it, while the outer remains stationary.