men before the time of Gall, yet to this great man is due the credit of having demonstrated that the brain is constituted of a number of organs with different functions.

Diagram 9 represents the base of the cerebrum and cerebellum, together with their nerves. 1. The anterior extremity of the fissure of the hemispheres of the brain. 2. The posterior extremity of the same fissure. 3. The anterior lobe of the cerebrum. 4. Its middle lobe. 5. The fissure that separates the anterior and middle lobes. 6. The posterior lobe of the cerebrum. 7. The point of the infundibulum. 8. Its body. 9. The corpora albicantia. 10. Cineritious matter. 11. The crura cerebri. 12. The pons varolii. 13. The top of the medulla oblongata. 14. The posterior prolongation of the pons varolii. 15. The middle of the cerebellum. 16. The anterior part of the cerebellum. 17. Its posterior part, and the fissure of its hemispheres. 18. The superior part of the spinal cord. 19. The middle fissure of the medulla oblongata. 20. The corpus pyramidale. 21. The corpus restiforme. 22. The corpus olivare. 23. The olfactory nerve. 24. Its bulb. 25. Its external root. 26. Its middle root. 27. Its internal root. 28. The optic nerve beyond the chiasm or crossing. 29. The optic nerve before the chiasm. 30. The third pair of nerves. 31. The fourth pair. 32. The fifth pair. 33. The sixth pair. 34. The facial nerve. 35. The auditory nerve. 36, 37, 38. The eighth pair of nerves.

The different parts of the brain, instead of receiving names expressive of the functions which they performed, have been named according to the shape which they generally assume.

THE BRAIN DIVIDED INTO TWO HEMISPHERES. 29

This accounts for the strange and unphilosophical terms which are used by writers on anatomy, and which are only calculated to discourage the common student. Indeed, few medical students think it worth the trouble to learn the details of the anatomy of the brain as it is commonly taught, as they soon ascertain that it is of no practical use; consisting of merely learning the locality of parts, the offices of which are unknown, and even unconjectured, and simply resembling in form certain familiar objects from which they derive their

Diagram 10.-a, a, Represents the scalp turned down. b, b, b, The cut edge of the bones of the skull. c, The external strong membrane of the brain, the dura mater, suspended by a hook. d, The left hemisphere of the brain, shewing its convolutions. e, The superior edge of the right hemisphere, f, The fissure between the two hemispheres.

Dr Gall's discovery threw great light on the anatomy and physiology of the brain, and scientific men have given names to many parts, expressive of their functions.

The brain and spinal cord are in two equal and symmetrical halves, called hemispheres, one of which is contained within the right side of the skull, and the other in the left. Every essential part that is found upon one hemisphere is

found in a corresponding place on the opposite. See Diagram 11. Thus phrenologists have discovered about forty organs of mind in one hemisphere, and a corresponding number of similar organs on the other side; thus upwards of forty

Diagram 11.-The Vertical Section of the Brain.

1 The cerebellum. 2, 2, 2, 2. The skull. 3. The frontal sinus. 4, 4, 4. The scalp. 5, 5, 5. The cerebrum. 6. The pons varolii. 7. The medulla oblongata. 8. The spinal cord.

nerves proceed from one hemisphere of the brain and spinal cord to different parts of the body, and an equal number proceed from the other hemisphere in a similar manner. This explains why nervous diseases sometimes affect one side of the face and body, and not the other.

The division of the great organs of mind into hemispheres corresponds with the fact that all the organs of the body that obey the mind are double; so also are the organs of the senses that carry information to the mind. Thus we have two hands, two feet, two eyes, &c. The body, and particularly the face, may therefore be said to be divided into right and left hemispheres; and in this is a good illustration of the manner in which the brain is divided. The line which divides the right from the left hemisphere is called the median line. The commissures of the brain are parts that

extend across from one hemisphere of the brain to the other, and are evidently intended to produce unity of action between them; so that although the great organ of the mind is double, the operations of mind are single; and notwithstanding the organs of sense are double, the sensations are single. One side of the head cannot be angry while the other is pleased; one side cannot delight in music while the other is averse to it; but both hemispheres act together, as if they were one, which could not possibly be the case if they were not intimately united by means of the commissures. The largest commissure is called the corpus callosum; this may easily be seen by separating with the fingers the two hemispheres of the uncovered brain; a white mass, several inches wide and about half an inch in thickness will then be seen extending across from one hemisphere to the other, like a bridge.

Mr Combe says that he pointed out a convolution of the brain lying above the corpus callosum, extending from the bottom of concentrativeness to the organs of the intellect. This convolution Mr Solly has shewn to be a commissure uniting the posterior and anterior portions of the brain. This gentleman describes nine commissures-six transverse, two longitudinal, and one oblique. The annular protuberance is about one-sixth the size of the corpus callosum, and extends from one hemisphere of the cerebellum, or organ of amativeness, to the other, passing across the medulla oblongata, in such a manner as to be called sometimes the bridge of Varolius, or pons varolii.

We can only conjecture the use of the two commissures from their situation; the fact, however, that they are not found in some classes of animals seems to indicate that they are not so important as their size would lead us to suppose. Dr Spurzheim mentions two cases where the corpus callosum was rent entirely asunder, yet the manifestations of mind of the individual did not appear to be at all affected by it. There are three commissures at the base of the brain, which Dr Spurzheim considered the true commissures. They are the anterior, the middle, and the posterior, each of which is about the size of a goose-quill, and they cross, one in the front, another in the middle, and the third in the back part of the brain. Besides these commissures there is one in front of the medulla oblongata—a decussation—that is, the

fibres cross from one side to the other in such a manner as to resemble plaited straw, the hemispheres being entirely separated from each other by a membrane, except where the commissures cross.

There are several parts in the median line which do not seem to belong to either hemisphere, and their uses are unknown. One of these is called the pineal gland, and is about the size of a pea. This is the celebrated part where Descartes fancied the soul to reside, and it is situated just above the posterior commissure, and seems to be attached to it. Just above the same place are four small round bodies, known by the name of the quadrigeminal bodies. There may be seen also in the median line, at the base of the brain, near where the optic nerves unite, two little round bodies, which, on account of their supposed resemblance to breasts, are called mamillary bodies; and near them is another, called the infundibulum, or funnel. The very names which these parts have received betray the total ignorance of anatomists concerning the offices which they perform.

The subdivisions of the hemispheres are into the cerebrum, the cerebellum, the medulla oblongata, and the spinal cord. The spinal cord is contained within the vertebræ or backbone, and extends from the lower part of the back, up to the medulla oblongata. It is considered by Sir Charles Bell as composed of three independent nervous columns, the anterior, the middle, and the posterior. The anterior column Bell considers as the medium through which the brain acts upon the muscles to produce voluntary motion. The middle he denominates the respiratory column, because it sends branches to all the organs of respiration, and the other parts that must act in harmony with them in speaking, laughing, crying, coughing, &c. He considers it as related to respiratory motion only, and not to sensation.

While we accord to Bell the merit of having first discovered that the spinal cord is composed of three columns, we cannot admit that he has proved that the middle column is exclusively devoted to respiratory motions, and the posterior to sensation. We doubt not that the principles unfolded in this work will lead to a more philosophical view of the true functions of these three columns, and their relations to the brain and body. Bell says "that the middle column stops short in the medulla oblongata, not being in function.