Popular Science Monthly/Volume 54/December 1898/Brain Weights and Intellectual Capacity
|BRAIN WEIGHTS AND INTELLECTUAL CAPACITY.|
By JOSEPH SIMMS, M. D.
HAVING been for thirty years a lecturer on man and his character as evinced by his form, features, head, and gestures, and having made observations on the subject in all parts of North America, in continental Europe and Great Britain, and parts of Asia, Africa, and Australia, I should not be deemed presumptuous when I present a few facts regarding the relations of mind and the size and forms of heads and weights of brains. It has been observed by many persons versed in the branches relating to the subject that men with the largest brains are not those of most talent, power, or intellect; but many such have been only ordinary or inferior men, or even idiots; while some men of most powerful and comprehensive minds have had unusually small brains. Esquirol's assertion that no size or form of head or brain is incident to idiocy or to superior talent is borne out by my observations.
After long and careful research in the great libraries and museums of the world, I have collected a table of brain weights of eminent men, along with which are entered, in my original document, the occupation of the subject, age at the time of determination, and the source whence the item is derived. These can not be given within the limits of this article, and only the briefest and most generalized summary of the main features can be indicated. The largest weight of brain in the whole list is that of the Russian novelist Turgenieff, whose brain weighed, at the time of his death, at sixty-five years of age, 71 ounces. It is a considerable step from him to the next in order, the English mechanician and author, Knight, whose brain weight at the age of fifty-eight was 64 ounces. Then follow the Scottish physician Abercrombie, 63 ounces; General B. F. Butler, 62 ounces; and the Scottish general Abercromby, 62 ounces. Another group of nine, including weights from 58.6 ounces to 54 ounces, includes Jeffrey, Scottish judge and author, Thackeray, Cuvier, George Combe, United States Senator Atherton, Spurzheim, and the Scottish physician Simpson. The next group, 53.6 to 50, is larger, including twenty-one names, among which are Daniel Webster, Agassiz, Napoleon I, the Scottish divine Chalmers, the mathematicians De Morgan and Gauss, the anthropologist Broca, and the generals Skoboleff and Lamarque. The last group, 49.9 to 40 ounces, contains twenty-five names, including those of the philosopher Huber, Grote, Babbage, the anthropologist Bertillon, Whewell, Liebig, Gall, Gambetta, and Bishop, the mind reader. Only one remove from the foot of the list is Gambetta, a man of indisputably high genius and ability, with a brain weighing only 40.9 ounces.
The table goes to illustrate a general rule which I discovered and published several years ago, that larger brains appertain to natives of colder climates. Dr. John Abercrombie, for instance, was born at Aberdeen, Scotland, on the German Sea, and farther nortb than any part of the United States. Sir Ralph Abercromby was born in the county of Clackmannan, Scotland, where it is far colder than any part of southern Europe. Lord Francis Jeffrey first saw light in Edinburgh. General Butler was born in Deerfield, New Hampshire. Ivan Turgenieff, with the heaviest brain of all, was a native of cold, inhospitable Russia. Dr. Franz Joseph Gall (brain weight 42.2 ounces) was born in Würtemberg, in southern Germany, passed most of his life in Vienna and Paris, and, being a student, spent much of his time indoors. Gambetta was born at Cahors, France, of Italian parents. This climatological view of the size of brains is confirmed by a paper, "Crania," of the Philadelphia Academy of Sciences, which gives as the average size, in cubic inches, of the cranial cavities of various nationalities, taking the results of many measurements: Lapps, 102; Swedes, 100; Anglo-Saxons, 96; Finns, 95; Anglo-Americans, 94; Germans, 92; Celts, 88; Malays, 86; Chinese, 85; Tombs of Gizeh, 84; embalmed Semitic, 82; Egyptians, 80; Fellah, 79; Bengalese, 78.
A table of average brain weights of various nationalities, compiled from Topinard's and Manouvrier's works and other standard anthropological publications, illustrates the same tendency toward greater brain weights in colder countries. One of its results is to show that the colder air of the United States produces larger brains in the negroes than the warm air of Africa. The table further shows, in the comparisons of Hindus and African negroes, that the brains are smallest in the warmest countries, irrespective of race or nation; and that the largest average attained is in Scotland, where it is never extremely warm.
The measurement of the cranial cavity is a very uncertain gauge of the size of the brain, for the cerebro-spinal fluid may occupy a large share of the space. Weighing the brain is without doubt the only scientifically certain method of determining its size and mass.
Perhaps the most remarkable case in the table of great men's brains is that of Gambetta, who was behind none of his compeers in ability, and yet had the smallest brain of all. The first table of the "Average Weight of the Human Body and Mind," compiled from Dr. Boyd's researches among the sane, which was based on more than two thousand post-mortem examinations, gives 45.9 ounces as the average brain weight of boys from seven to fourteen years of age, and 40.2 ounces as that of boys and 40.1 ounces of girls from four to seven years of age. And this little brain of 40.9 ounces appertained to a man, "a lofty, commanding, mental figure, standing out in bold relief from the crowd of mediocrities which he dwarfs and shadows," the embodiment of the French Republic, who steered it through one of its most perilous crises, "the foremost Frenchman of his time," who "established his claim to be placed in the very front rank of European statesmen," and whose untimely death was spoken of as "nothing less than the sudden extinction of a powerful individual force, one of the most powerful, indeed, of such forces hitherto operating in Europe."
In illustration of the association of large brains with small minds, we have compiled from various sources of recognized authority a list of one hundred and twenty-five persons of ordinary or weak minds, idiots, imbeciles, and criminals, whose brains were generally larger than those of the distinguished men subjects of the preceding notes. Of these, Rustan, an ignorant and unknown workman, appears with a brain weighing 78.3 ounces; the dwarfed Indian squaw who follows him, of 73.5 ounces; an illiterate and weak-minded man had a brain of 71.3 ounces; and a congenitally imbecile person cited by Dr. Ireland, with one of 70.5 ounces. Another imbecile cited by Dr. Ireland had a brain of 63.2 ounces, and the brain of an idiot with a large head, eighteen years old, who had an idiotic sister, weighed 62.8 ounces. The brain of the idiot, No. 56 of the men in the table, 59.5 ounces, is exceeded in size by those of only five on the list of famous men, while eleven persons recorded as idiots, imbeciles, and children had brains heavier than his. An idiot boy of fourteen years, very malicious, who never spoke, and who nearly killed his sister with a pick, had a brain weight of 57.5 ounces. Thirty men out of three hundred and seventy-five examined in the West Riding Asylum gave brain weights of 55 ounces and upward, showing that such weights are not so rare as some have supposed. In another asylum in England one out of every dozen brains examined showed a weight of 55 ounces or more.
In Nachrichten, of Göttingen, 1860, pp. 70-71, Dr. Rudolph "Wagner gave a table of thirty-two persons whose brains he examined, among whom were five distinguished men; but the largest brain weight recorded in it, 55.9 ounces, has opposite to it the legend, "Idiotic grown man."
To this list we might have added a large number of persons whose brains weighed less than 53 ounces. Yet the brains of Daniel Webster, Agassiz, Napoleon I, Lord Byron, Baron Dupuytren, General Skoboleff, and other famous men concerning whose large brains much has been said, weighed less than this; and we might have appended hundreds of brain weights of idiots, imbeciles, and other insignificant persons, from 53 ounces down to 49 ounces—probably about the average weight in central Europe. In support of our contention is, further, an observation by Dr. Rudolph Wagner in Nachrichten, February 29, 1860, pp. 71, 72, that "very intelligent men certainly do not differ strikingly in brain weight from less gifted men."
Dr. Clendenning presents in the Croonian Lectures the following entries of brain weights of male subjects of different ages, the tendency of which is to show that the male encephalon loses, after it is grown, more than an ounce every ten years:
A number of other eminent anatomists have given similar evidence of decrease in brain weight as intellectual power increases.
The "Professor at the Breakfast Table," the late Dr. O. W. Holmes, a learned man and experienced physician and professor of anatomy in Harvard University for thirty-five years, says: "The walls of the head are double, with a great chamber of air between them, over the smallest and most crowded organs. Can you tell me how much money there is in a safe, which also has thick walls, by kneading the knobs with your fingers? So, when a man fumbles about my forehead, and talks about the organs of individuality, size, etc., I trust him as much as I should if he felt over the outside of my strong box, and told me that there was a five-dollar or a tendollar bill under this or that rivet. Perhaps there is, only he doesn't know anything about it. We will add that, even if he knows the inward dimensions of the strong box, he could not thence determine the amount of cash deposited in it."
The internal size of Spurzheim's skull was in cubic inches exactly the same as that of the skull of Joachim, an imbecile six feet nine inches in height, with a brain weight of 61.2 ounces, whereas Spurzheim's brain weighed only 55 ounces.
Whoever has examined heads in the dissecting room of a medical college knows that, except in rare cases of disease, the brain does not fit the skull, but is surrounded by three membranes and a watery fluid; and this liquid, it has been ascertained, is generally sufficient to admit of its performing certain movements.
There can be no doubt that the brain moves in the skull, changing its position, according to the laws of gravitation, in much the same way as the lungs, heart, and liver do in the body. It has been observed many times to move, as well as to pulsate, when exposed to view during the life of the individual. It is subject to two regular and constant motions—one produced by the arteries, the other by respiration. It has also a third motion, discovered and described by Dr. M. Luys, who stated, in a paper read before the Academy of Medicine of Paris, that "the brain is subject to certain changes of position, dependent on the attitude of the body. Thus, if a man lies on his back or side, or stands on his head, the brain undergoes certain changes of position in obedience to the laws of gravity; the movements take place slowly, and the brain is five or six minutes in returning to its previous position." From these anatomical data M. Luys deduced some interesting and practical conclusions, by which he explained, for example, the symptoms of vertigo which feeble persons experience when suddenly rising from a horizontal position. He suggested whether the pains of meningitis may not be due to an interference with these normal movements, and urges the value of giving the brain the change produced by a horizontal position at night.
The average cranial capacity is admitted to be 96 cubic inches in England and 94 in New York; and it is to the unusual quantity of fluid of some cases, and to the extraordinary thickness of the skull in others, that we are to attribute the frequent discrepancy between the external dimensions and the size of the encephalon. Daniel Webster's cranial capacity was 122 cubic inches, yet his brain of 53.5 ounces was just what George Combe has laid down as the average weight for an adult man. Water and lymph, we are told, filled the skull. Professor De Morgan's head, almost free from hair, measured 24.87 inches in circumference, and the dimensions were all those of a very large head, sufficient to contain from 65 to to ounces of brain, yet his brain weighed only 52.75 ounces, or little, if at all, above the average in the cold parts of the temperate zones. De Morgan was sixty-five years of age when he died. He was much emaciated, and "the brain was distinctly shrunken," not filling the interior cavity, where its place was supplied, as is usual in such cases, by serum or water. There is no known method whereby any man can determine whether brain or water fills the greater part of any living skull. A small orange may have a thin rind, and contain a good amount of eatable substance, while a large one may have so thick a skin that the fruit proves utterly disappointing.
Another proof that the skull is formed without regard to the brain is the following: "The bony cabinet and its contents are developed, to a certain extent at least, independently. This is very clearly demonstrated by a fact which was observed by Gratiolet, and is too frequently forgotten. The subject is an infant in whom the cranium presented the normal conformation. The brain was, nevertheless, almost entirely wanting."
Dr. Gall was a poor arithmetician, and his biographer says that every kind of numerical calculation fatigued him. He could not go through a process of multiplication or division that was at all complicated, and knew nothing of geometry or of the problems of mathematics. George Combe said of himself: "Arithmetic has always been to me a profound mystery, and to master the multiplication table an insurmountable task. . . . This faculty in me is, in fact, idiotic." Again he said: "When a boy, I never could learn arithmetic. At the end of five years' teaching I could not subtract, divide, or multiply any considerable number of figures with accuracy and facility, and can not now do so. . . . At the present day I can not sum a column of figures correctly."
With these facts in view, our wonder at finding the theories of these men at variance with all exact calculation is considerably diminished. We propose to test some of their theories by arithmetical processes. We found that the sixty famous men entered in the table of authenticated brain weights show an average of 51.3 ounces. We now take all the idiots and imbeciles in the table of "Large Brains and Small Minds," and find the average 59.4 ounces; so that the matter is left to stand thus: Ten idiots and five imbeciles average 59.2 ounces; sixty famous men average 51.39 ounces: in favor of idiocy and imbecility, 7.9 ounces.
The heaviest brain in the table of small minds is that of Rustan, an ignorant and entirely unknown laborer. He was a healthy man, and his brain, when it was weighed, was in a healthy condition. Its weight was recorded by Dr. Carl A. Rudolphi, a Swedish naturalist and physiologist of Stockholm, who became professor of anatomy and physiology at Berlin in 1810. It reached the unexampled figure of 78.3 ounces; while the brain of Turgenieff, the heaviest among famous men, was 71 ounces—showing a difference of 7.3 ounces in behalf of the inferior mind.
Since writing the above, the following appeared in Tit-Bits, a weekly paper published in London, England, March 19, 1898:
"It must not be assumed, however, that intellect is in direct ratio to the weight of the brain; for while the brains of certain intellectual men, such as. . . Dr. Abercromby, weighed more than 60 ounces, a certain Strand newspaper-boy, who was in intelligence almost an idiot, had a brain which weighed no less than 80 ounces."
Dr. Austin Flint, of New York, in his Physiology, gives the average weight of the brains of men as 50.2 ounces. Dr. Peacock, of Great Britain, makes it 50 ounces 3 drachms between twenty-five and fifty years of age. Dr. Thurman gives 49 ounces as the average throughout Europe, while Dr. F. Tiedemann, a famous naturalist of Germany, reckons it at 53.2 ounces. Dr. Krause, a learned German, places it still higher, at 55.4 ounces. Now, if we strike a balance between the highest and the lowest of these estimates, the mean will be 52.2. Then, recalling the average of our sixty famous men, which we found to be 51.3 ounces, it is shown to be nine tenths of an ounce below the average of ordinary men.
Our tables of national average brain weights do not quite agree, because some of the subjects had been wasted by disease for many months before death, whereby the brain was diminished along with other parts of the body. Those who, like Dr. Boyd's subjects, died in hospital, showed too light an average for healthy Englishmen. Dr. Krause's subjects may have been healthy men killed in battle, and those of Tiedemann persons who died suddenly. Executed criminals show a fairly high average of brain weight, because there has been in their case no diminution through long-continued illness. We should recollect that Whewell, the famous English philosopher and head master of Trinity College, Cambridge, England, was in good health when killed by a fall, from his horse; so was Gambetta, when his life was ended by a pistol shot. The brain, however, suffers less from the power of disease than the general bodily form. One month under the most wasting sickness would probably not diminish the brain more than an ounce or two, but a year or more would make a considerable difference.
Taking, now, the sixty heaviest brains of persons not noted for intellectual greatness, we find the averages to be 63.2 ounces. Comparing this with the average of sixty famous men, 51.3 ounces, we find a difference in favor of imbeciles, idiots, criminals, and men of ordinary mind of 11.9 ounces. George Combe estimated that about 53.5 ounces was the average weight of the adult brain. Thus the average brain weight of all the eminent men whom we have brought into the comparison, 51.3 ounces, is below Combe's estimate of that of mankind in general. Again, the ten heaviest brains of our list of famous men give an average weight of 61.1 ounces, while the average given by the ten heaviest of the opposite class is 70.4 ounces, or 9.3 ounces greater. While our list of eminent men shows only five whose brains exceeded 58.6 ounces in weight, those of seventy-six of the common throng—seven of them idiots or imbeciles—rise above that figure. These figures augur badly for the doctrine that would attach importance to heavy brains for giving force and depth of individual character.
Phrenologists assert that each organ of a mental faculty occupies a certain position perceptible on the outside of the brain, with a definite area which they have mapped out. .They also hold that each of these organs extends to the center of the base of the brain, tapering to it somewhat like a cone, having its base turned toward the outer world. They make no account of the fissures, the intervening sulci and anfractuosities that must cut many of these supposed cones, some at right and some at oblique angles. Then the large, long cavities or ventricles intercept and would hinder many of them from reaching the central, basilar part of the brain. The anatomical structure of the brain thus appears fatal to this theory of the organs.
Large and complicated convolutions of the brain with deep sulci have been regarded by some persons as inseparable from superior powers of mind. The supposition is erroneous and groundless. The rodents, such as beavers, squirrels, rats, mice, etc., have but little brain and no convolutions whatsoever; yet the beaver exhibits great foresight, economy, industry, and mechanical skill in building his dam, erecting his house, and storing up bark as food for the winter. Moreover, these animals live in societies and labor in union by ingenious methods for a common purpose, with nice judgment. "So great a variety of labors," says Dr. Leuret, "is needed for the constructions carried on by the beaver; they include so many instances of well-made choice, so many accidental difficulties are surmounted by these animals, that it is impossible not to recognize in their actions the characteristics of a rather high intelligence." The sheep has a much larger brain than the beaver, with numerous and complete convolutions, yet it is one of the most stupid of domestic animals. Again, though birds have convolutions in the cerebellum, they have none in the cerebrum, and yet they are more capable of education than any living beings except the human race. The eagle is complete master of the lamb; the magpie, the hawk, the raven, and the parrot with his talking powers, are not excelled in sagacity by the dog, the horse, or the elephant, notwithstanding the latter animals have brains of superior size and elaborate convolutions.
Squirrels manifest foresight and economy in storing nuts for the winter's use; yet they have no brain convolutions. The cetacea, especially whales, have much larger brains than men, with more numerous and more complex convolutions and deeper sulci; yet their intelligence bears no comparison with that of the human race.
Three eminent men are known to have had very small convolutions of the brain—viz., Louis Asseline, Dr. Tiedemann, and Baron von Liebig. We have to add to this remarkable list two, not named, but described by Dr. Wagner as having been very intelligent, who yet possessed very few convolutions in their very small brains. As Wagner's book was printed before Liebig died, he could not have been one of the two to whom the author referred.
Idiots often possess as large brains as men distinguished for intellectual power, and their brains have as deep sulci, and convolutions as fine, as large, and as complex. Our table of the common and weakminded contains a mention of an idiot whose brain weighed 53 ounces, or exactly as much as Napoleon's, and had fine convolutions and a large frontal lobe, but who could never learn to speak.
The elephant carries a far larger brain than man, finely formed, broad and high in front, with much more numerous and complex convolutions and deeper anfractuosities, and yet no intelligent person would for a moment claim that its mind excels or even equals that of man.
It may be well here to allow some eminent physiologists to give their views on this subject. "The researches of anatomists have disposed of every point advanced by Gall. Curiously enough, M. Camille Dareste has placed beyond dispute the fact that the number and depth of the convolutions bear no direct proportion to the development of intelligence, whereas they do bear a direct proportion to the size of the animal. . . . It is notorious that the instinct of propagation, the instinct of destructiveness, the instinct of constructiveness, and other qualities are manifested by animals having no brains, nothing but simple ganglia."
Dr. Bastian demonstrates the convolutional theory thus: "In animals of the same group or order, the number and complexity of the convolutions increase with the size of the animal. . . . There can not, therefore, be among animals of the same order any simple or definite relation between the degree of intelligence of the creature and the number or disposition of its cerebral convolutions."
We have the following testimony in our favor from Dr. Rudolph Wagner, of Göttingen: "Examples of highly complicated convolutions I have never seen, even among eminent men whose brains I have examined. . . . Many convolutions and great brain weight often go together. Higher intelligence appears in both kinds of brains, where there are many or where there are few convolutions. It is not proved that special mental gifts go with many convolutions."
Another theory of mind is based on the gray matter of the brain, the amount of which has been supposed to be proportionate to mental capacity. As this gray matter, however, averages only about one fifth of an inch in thickness, it seems rather a thin foundation for the human intellect if the condition is good that "size is a measure of power."
The late Dr. W. B. Carpenter stated the matter thus: "The cortical substance or gray matter of the hemispheres essentially consists of that vesicular nerve substance which, in the spinal cord as in the ganglionic masses generally, is found to occupy the interior. The usual thickness is about one fifth of an inch; but considerable variations present themselves in this respect, as also in the depth of the convolutions."
Daniel Webster's brain had gray substance to the depth only of one sixteenth of an inch. It thus appears that his brain had a thinner layer of gray matter than the average of common-minded men—one among the many proofs that facts are against all theories that connect brain conditions with intellectual power.
Dr. Ireland thus describes an idiot boy who, though thirteen or fourteen years of age, was only three feet eight inches in height: "In expression he was dull and inanimate, with an old face and a short, squat figure. . . . The convolutions were broad and simple, but not shallow. The gray matter was as broad as usual."
The writer has examined many brains of persons morally or intellectually below the average—such as murderers, negroes, and others sunk in ignorance. He has invariably found the layer of vesicular or gray matter to be thicker than that of Daniel Webster's brain. Elephants, porpoises, whales, dolphins, and the grampus all have this layer thicker than the most intellectual men. Another great objection to locating mind in the gray matter of the brain is that this substance is found in the interior part of the spinal cord, and in all the nerve centers throughout the body; so that, if mind is situated in it, it is not confined to the brain, but dwells in the spine also, and is distributed all through the human frame. Still another objection lies in the fact that wherever the gray matter exists near the surface of the brain, it consists of three distinct layers, separated by a white substance, and the outermost layer is white, not gray.
The septum lucidum consists of gray matter. The corpus striatum, situated at the base of the lateral ventricles, nearly in the center of the brain, was from three eighths to half an inch in diameter in an ox which was dissected in Edinburgh. This is about the same amount as is found in the corpus striatum of the human brain. There would be lively times if it were possible for a mental faculty to occupy at once all the localities where gray matter is found!
None of the suppositions about certain qualities of mind inhering in particular portions of the brain have been proved, nor have they stood the tests of science.
The theories which have assumed that the cultivation of the intellect gives shape and size to the brain within and consequently to the skull without, advocates of which have not been wanting, have been disproved by the collected facts. "There is no proof," says Dr. J. O. Nott, in his Types of Mankind, "of the theory that the cultivation of the mind or of one set of faculties can give expansion or increased size of brain. The Teutonic races, in their barbarous state, two thousand years ago, possessed brains as large as now, and so with other races."
The St. Louis Globe Democrat of November 13, 1885, gives an account of some excavations on the Mount Ararat farm, east of Carrollton, Illinois, where the bones of thirty-two Indians or mound builders were unearthed. "They were not a diminutive race, as some people have supposed, some of the thigh bones being sixteen inches long, and some of the skulls twenty-four inches in circumference." A skull having a circumference of twenty-four inches means a head that measured from twenty-five to twenty-six and a half in life, when the cranium was covered with skin and muscles. The average head of white men in New York to-day is only twenty-two and a half inches round. So the culture of the white race for centuries has not developed their heads to near the size of those of the uncultured mound builders who inhabited America many centuries ago. Our own opinion is that cultivation by means of a thorough classical education, where the appetite is restrained, as usually occurs, tends rather to diminish the size of the head, by reducing the temporal muscles and the adipose tissue under the scalp.
The Engis skull is one of the most ancient known to exist, and belonged to the stone age, or about the same time as the Neanderthal skull. Professor Huxley describes it as being well formed, and considerably larger than the average of European skulls to-day in the width and height of the forehead and in the cubic capacity of the whole.
Quatrefages, in The Human Species, p. 312, says: "This skull (the Engis or Cro-Magnon), so remarkable for its fine proportion, is also remarkable for its capacity. According to M. Broca, who could only work under precautions calculated to diminish the amount, it is equal to at least 1,590 cubic centimetres (96.99 cubic inches). I have already remarked that this number is far higher than the mean taken from modern Parisians; it is equally so in comparison with other European nations."
These facts all conspire to prove that the cultivation of thousands of years has not increased the size of human skulls. In 1886, we measured many of the skulls unearthed at Pompeii, the remains of Romans who lived nearly two thousand years ago, and we found them on the average larger in every way, but especially in the forehead, than the skulls of Romans of this century.
In the museums of Switzerland we measured in 1887 several skulls of the ancient lake dwellers of that country, and found them larger in all respects, but particularly in the forehead, than those of the Swiss people of the last fifty years. The average circumference of the skulls we measured in the catacombs of Paris was twenty-one inches and a half, which is about an inch more than that of Parisians who have died within the past fifty years.
"The average internal capacity of the Peruvian skull is only seventy-three cubic inches; that of Toltec skulls, seventy-seven inches, and that of barbarous tribes, eighty-two inches; so that the extraordinary anomaly is presented of a larger brain being possessed by the barbarous tribes than by the nations who achieved no mean degree of civilization in Central America and Peru. The average European skull is ninety-three inches in bulk." The author was informed by Mr. Lucien Carr, of the Ethnological Museum of Harvard University, that the capacity of the Peruvian skulls was about one hundred centimetres smaller than that of the skulls of any other people living in America at the same time. Yet that small-headed people was the most highly civilized of all.
- Medical Times and Gazette, London, England, November 17, 1883.
- Whewell also had "the scalp and skull thick." Brain weighed 49 ounces. The Lancet, London, England, March 11, 1866, p. 280.
- Medical Times and Gazette, London, England, May 12, 1883, p. 525.
- London Medical Gazette, London, England, September 13, 1828, p. 478
- Brain Weight of Man. By Dr. Bischoff. Bonn, Germany, 1880, p. 137.
- Authority for this weight is the Medical Army Museum, Washington, D. C.
- This brain is kept in and its weight is recorded on the glass jar in the Pathological Museum at Munich, Germany.
- Idiocy and Imbecility. By Dr. Ireland. London, 1877, p. 75.
- The Human Species. By A. De Quatrefages. D. Appleton and Company, New York, 1884, p. 380.
- Dr. Gall's works, Boston, Massachusetts, vol. i, p. 36.
- Life of George Combe, London, 1878, vol. ii, p. 381.
- Medical News and Gazette, London, June 16, 1888, p. 521.
- Morning Herald, Sydney, Australia, February 23, 1884.
- Eleven Chinamen, found by Dr. C. Clapham to afford an average of 50.4 ounces, had been killed in a typhoon, and were therefore in no wise wasted by disease. (Journal of the Anthropological Institute, London, England, vol. vii, p. 90.)
- The Nervous System, London, 1834, p. 447.
- Anatomie comparative du système nerveux, tome i, 1839, p. 506.
- Ueber die typischen Verschiedenheiten der Windungen der Hemisphären und über Lehre von Hirngewicht, Göttingen, 1860. Also see Pathology and Therapeutics of Mental Diseases, London, 1870, p. 23.
- History of Philosophy, London, 1867, vol. ii, p. 433.
- The Brain as an Organ of Mind, London, 1880, pp. 276, 277.
- Nachrichten, Göttingen, February 29, 1860, p. 75.
- Carpenter's Principles of Human Physiology, London, 1881, p. 659.
- Edinburgh Medical and Surgical Journal, 1853, vol. lxxix, p. 360.
- Idiocy and Imbecility, London, 1877, pp. 216-219.
- See The Brain as an Organ of Mind, London, 1880, p. 465; also, The Human Brain, London, 1847, pp. 288, 289.
- Eclectic Magazine, December 14, 1863, p. 428.