science. While the weight of the entire brain is only about one forty-second of the weight of the body, it has been calculated that the supply of blood used by the brain is one eighth of that used by the whole body. How essential this supply of blood is, becomes evident if it is in any way interfered with. Stop one of the great arteries leading to the brain by compression in the neck or in any other way, and great disturbances in consciousness at once appear, even to the point of its entire cessation. One investigator, Dr. Lombard, found that the temperature of the head varies rapidly, though slightly, during waking hours. By careful measurements with delicate thermoelectric apparatus he found that "every cause that attracts the attention a noise, or the sight of some person or other object-produces elevation of temperature. An elevation of temperature also occurs under the influence of an emotion, or during an interesting reading aloud."1

Mosso's Table. If it were possible to doubt that this rise in temperature is due to an increase in the blood supplied to the brain, that possibility would seem to be removed by the experiments of an Italian investigator named Mosso. He devised a table so accurately balanced that a man might recline on it without disturbing its balance. He found that its balance was at once destroyed by any cause that quickened the activity of the subject's consciousness. A sudden noise, an interesting thought, anything that increased the activity of consciousness, would cause the head end of the table to sink down as quickly as if a weight had been placed upon it.

1 Quoted by Ladd, Physiological Psychology, p. 242.

Localization of Cerebral Functions.

All the argu

ments in support of what is called the localization of cerebral functions are so many arguments to show that the brain is the organ of the mind. These arguments we will consider in a later chapter. Suffice it here to say that it has been proved to the satisfaction of physiologists and psychologists, not only that the brain is the organ of mind, but that particular parts of the brain are connected in a peculiarly close and intimate way with certain mental activities. Evidently every argument in support of this conclusion is equally good to show that the brain is the organ of the mind.

A large number of experiments made upon the lower animals prove the same fact. First one part and then another of the brain of various lower animals (frogs and pigeons, for example) has been removed for the purpose of ascertaining what part of the brain is connected with particular classes of mental operations. And though the phenomena vary with the animal, and with the part of the brain removed, to say nothing of the skill of the operator, the facts taken together leave no doubt of the special connection between the brain and the mind.

The American Crow-bar Case. - For obvious reasons such experiments have not been performed upon the brains of men, but disease and accident have performed them for us. One of the most famous of these experiments is that which is now known as the American crow-bar case. While a young man named Gage was "tamping a blasting charge in a rock with a pointed iron bar, 3 feet 7 inches in length, 1 inches in diameter, and weighing 13 lbs., the charge suddenly exploded. The iron bar, propelled with its pointed end first, entered at the left angle of the

AMERICAN CROW-BAR CASE.

21

patient's jaw, and passed clean through the top of his head, near the sagittal suture in the frontal region, and was picked up at some distance covered with blood and brains. The patient was for a moment stunned, but, within an hour after the accident, he was able to walk up a long flight of stairs and give the surgeon an intelligible account of the injury he had sustained. His life naturally was for a long time despaired of; but he ultimately recovered, and lived twelve and a half years afterwards. . . . The whole track of the bar is included in that region of the brain. which I have described as the præfrontal region. Hear what Dr. Harlow (in a paper read in 1868 before the Massachusetts Medical Society) says as to his mental condition: 'His contractors, who regarded him as the most efficient and capable foreman in their employ previous to his injury, considered the change in his mind so marked that they could not give him his place again. The equilibrium or balance, so to speak, between his intellectual faculties and animal propensities seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference to his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned in turn for others more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previously to his injury, though untrained in the schools, he possessed a well-balanced mind, and was looked upon by the people who knew him as a shrewd, smart business man, very energetic and persistent in executing all his

plans of operation. In this regard, his mind was radically changed, so decidedly, that his friends and acquaintances said he was no longer Gage.'"1

Impairment of Memory Due to Injury of the Brain.It is a matter of common knowledge that injuries to the brain often result in an impairment of memory. Forbes Winslow notes a remarkable case of a soldier upon whom the operation of trephining had been performed and who lost a portion of his brain. The result was that he forgot the numbers five and seven, and those only. After a time his memory of these numbers was restored. Numerous cases are on record of the impairment of memory in consequence of a violent blow on the head.

Aphasia. — Very significant as to the dependence of mind on brain are the phenomena designated by the general term aphasia. Dr. Bateman says the term is used "to designate that condition in which the intelligence is unaffected, or at all events but slightly impaired; when thoughts are conceived by the patient but he can not express himself, either because he has lost the memory of words, or because he has lost the memory of the mechanical process necessary for the pronunciation of these words; or because the rupture of the means of communication between the gray matter of the brain and the organs, whose co-operation is necessary to produce speech, does not allow the will to act upon them in a normal manner as the ideas are formed, but the means of communication with the external world do not exist."

"2

1 Quoted by Calderwood in The Relations of Mind and Brain, pp. 479– 481, from Ferrier's Localization of Cerebral Disease. 2 Quoted by Calderwood, p. 388.

Motor Aphasia. — The foregoing definition, as we shall see in a later chapter, covers phenomena widely different from each other. A man who can understand what is said to him, but who can not talk, is said to suffer from motor aphasia. He knows what he wants to say, but he has lost control of the mechanism of speech. Sufferers from another kind of aphasia have perfect control of the mechanism of speech. They can talk, but they can not under stand what is said to them. They can hear, but they can not grasp the meaning of what is said to them.

Now in cases of motor aphasia it has been proved that the cause of the difficulty is located in a definitely ascertained part of the brain. Says Professor James: "Whenever a patient dies in such a condition as this and an examination of his brain is permitted, it is found that the lowest frontal gyrus is the seat of injury."

Correspondence between Size and Weight of Brain, and Intelligence. Still another class of facts may be pointed out as indicating the closeness of the relation between the mind and the brain. Comparative anatomy shows that there is a general, though indefinite, correspondence of the place of an animal in the scale of intel ligence, to the size and weight of its brain compared with the bulk of its entire body. In other words, as a rule, the larger and heavier the brain of an animal in comparison with the weight of its entire body, the higher it is in the scale of intelligence. As Professor Ladd says, "The law itself is confessedly subject to remarkable and unexplained exceptions; at best it only holds good in a general way. For example, the relative weight of the brain is not greatly different in the dolphin, in the baboon, and in