BRAIN. CEREBRUM.-CEREBELLUM.-SPINAL MARROW.

teries appear to possess a higher degree of irritability. Glands appear to the eye as whitish membranous masses.

The BRAIN consists of the whole of that mass which, with its surrounding membranes and vessels, fills the greater part of the skull. It is said to be larger in man, in proportion to the nerves belonging to it, than in any other animal. It consists of the cerebrum, cerebellum, tuber annulare, and medulla oblongata; the whole weighs usually about forty-eight or fifty ounces; but its weight varies in different subjects.

The CEREBRUM, which is by far the largest portion, is contained in all the upper part of the skull; it is divided into a right and left hemisphere by a membrane termed falx. Each hemisphere is also again subdivided into three lobes, the two lying in the front portion of the skull being the largest. It is surrounded with membranes, and accompanied with blood-vessels.

The CEREBELLUM, or little brain, is situated in the back part of the skull beneath the posterior lobes of the cerebrum, from which it is separated by a membrane called the tentorium. It is divided by the falx minor into two hemispheres, which are again subdivided into lo.

bules.

The Tuber annulare is of a roundish form, about an inch in length and of the same width. From the tuber annulare arises the medulla oblongata, which forms the beginning of the spinal marrow.

From the Brain arise nine pairs of NERVES; some in solid cords, others in separate threads which afterwards unite into cords. Of these some have their origin in the cerebrum, some in the cerebellum, some in the tuber annulare, and some in the medulla oblongata. From these the nerves supplying the organs of smell, sight, taste, hearing, and feeling, in part, are derived. The nerves are called pairs, not because they proceed together from the brain and spinal marrow, but because they proceed from the opposite lobes of the brain, or from opposite sides of the spinal marrow, and supply similar parts on each side of the body with nerves. And hence it often happens in paralysis, or palsy, that on one side of the body all the nerves perform their office imperfectly, while on the other side no diminution of nervous energy is evinced. A nerve is a long white medullary cord. The uses of the nerves are to convey impressions to the brain, from all parts of the body, over which they are spread, and to impart motion, by exciting the muscles, to the whole system. It is the opinion of some philosophers, that the nerves contain a subtle fluid, by means of which impressions are immediately carried to the brain: this fluid has, however, never been seen others think that sensation is produced by what has been termed vibration; but the plain truth is, we are at present ignorant of the means by which sensation and muscular motion are produced, further than that we know both are the effect of the agency of the nerves.

The SPINAL MARROW, or medulla spinalis, is a continuation of the medulla oblongata from the head through the centre of the spine, which consists of a series of bones called vertebræ supporting the body. From the spinal marrow are given out thirty pairs of nerves: these, in conjunction with those arising from the brain, communicate energy and feeling to the whole body; and also by their extreme sensibility

SPINAL MARROW.

convey to the brain, the mind, or soul, the slightest as well as the strongest impressions made upon the different organs; hence our pleasures and our pains, our hopes, our fears, and our affections.

That the Brain, as a whole, is the organ of thought, the seat of the understanding, and the place where the emotions of the mind or soul arise, we cannot doubt; it is also the centre of sensation and muscular motion, and to which all the nerves of the body appear subservient. But to what other particular uses the different parts of the brain are applied, does not yet appear accurately known.

Phrenologists have pretended to throw some light on this curious and interesting subject. We shall confer a favor on our readers, we trust, by making them acquainted with some of the results of their investigation.

The founder of the system of phrenology-by which is meant, "the science which treats of the faculties of the human mind, and of the organs by which they manifest themselves," is Dr. Gall, a physician of Vienna, who, about the year 1796, first began to deliver lectures on the subject. In 1804, Dr. J. G. Spurzheim became associated with him. Under the auspices, and captivating eloquence of these gentlemen, the system has acquired some credit, in several parts of Europe.

For ourselves, we give little credit to it. Its tendency is obviously towards the gloomy and foolish doctrine of materialism. In one respect-in regard to the position, and size of the brain-there is truth in phrenology; but, of the particular mapping of the skull, as adopted by the phrenologists, we think it behooves us, at present, to remain in modest doubt.

Still, as a subject of curiosity, it is not without interest. And in order that our readers may judge, in respect to themselves, what is the strength of their intellectual powers, or to what propensities they are most inclined, we have engaged our engraver to execute the outlines of a human head, skilfully and scientifically divided up, or mapped out, in the language of the science. The reader will notice that in each division is supposed to lie some faculty, or propensity of the mind. By an inspection of the brain itself, or the living man's head, the phrenologists affect to determine what faculty or propensity predominates -whether a man is gifted with the love of study, or inclined to idleness-whether he is peaceful or quarrelsome-timid or courageous-a wise man, or a fool. We leave our readers to apply the subjoined rules for themselves.

The numbers which follow, refer to the numbers to be found in the maps of the heads below.

1. Here lies the propensity of amativeness or physical love. 2. Here, the propensity of philo progenitiveness, or love of children. 3. Concentraveness, or power of close study, (not represented.) 4. Adhesiveness, or disposition to friendship. 5. Combativeness or quarrelsomeness. 6. Destructiveness, or desire to destroy, and murder. 7. Constructiveness, or mechanical skill. 8. Acquisitiveness, disposition to avarice, theft, &c. 9. Secretiveness, cunning, deceit. 10. Self-esteem, on the top of the head, (not represented.) 11. Love of approbation, in the same vicinity. 12. Cautiousness. 13. Benevolence. 14. Veneration. 15. Hope. 16. Ideality, or love of the sublime. Fine arts. 17. Wonder. 18. Consci

The THORAX or CHEST consists of the upper portion of the trunk of the human body; it is inclosed by the ribs, having the sternum or breast bone in the front, and a portion of the bones of the back behind. It is separated from the liver, stomach, intestines, &c., by the diaphragm, or nidriff. The thorax contains the lungs, heart, &c., and numerous blood vessels, nerves, and absorbents. It is also separated, by a membrane called mediastinum, into a right and left portion.

The RESPIRATION is that action of the lungs and diaphragm consisting of the processes of inspiration and expiration, by which air is received into, and expelled from the thorax or chest. The quantity of air taken into the lungs at each natural inspiration is supposed to be about 15 or 16 cubic inches; the number of respirations made in a minute is about 20.

WINDPIPE.LUNGS.-HEART.

The WINDPIPE is a cartilaginous and membranous canal, through which the air passes into and from the lungs. It is divided by anatomists into three parts, the larynx, the trachea, and the bronchia.

The larynx is a hollow cartilaginous organ at the top of the trachea. The air which passes through it during respiration produces the voice. The trachea, is that portion of the wind-pipe which extends from the larynx to the bronchia.

The bronchia is a term given to the trachea after it has entered the thorax, or chest; here it separates into two branches, one of which communicates with the right and the other with the left lung.

The LUNGS are two viscera situated in the thorax, by means of which we breathe. The lung in the right cavity of the chest, is divided into three, that in the left cavity into two lobes. They hang in the chest, attached at their superior part by means of the trachea, and are separated by a membrane called mediastinum. They are furnished with innumerable cells which are formed by a continuation of the trachea, the bronchial tubes of which communicate with each other; the whole appears not unlike a honey-comb.

The most important use of the lungs is for the process of respiration, by which the circulation of the blood appears to be immediately supported; and, doubtless, by their alternate inflation and collapsing, they contribute with the diaphragm to promote the various functions of the abdominal viscera, such as digestion, &c. For the change which the blood undergoes in its passage through the lungs, see the following articles.

The HEART is a hollow, strong, muscular viscus, having the shape of a cone or pyramid reversed. Its size varies in different subjects; it is generally about six inches long, and, at the base, four or five wide. The younger the subject, the larger is the heart, in proportion to the body. It is often smaller in tall and strong men than in others. It is situated on the left side of the thorax, and is surrounded by a membrane called pericardium or heart purse; it is also imbedded, as it were, in the left lung. Its weight, with the pericardium, is usually from ten, to fifteen ounces. It is the centre of the circulation of the blood: of course from it all the arteries arise, and in it all the veins terminate. It is divided internally into a right and left ventricle; these are divided by a fleshy septum. Each ventricle has two orifices; one auricular, through which the blood enters, the other arterious, through which the blood passes out. These four orifices are supplied with valves. There are also two cavities adhering to the base of the heart called auricles. The heart has, in the living subject, an alternate motion consisting of contraction and dilatation, called systole and diastole, by means of which the blood is circulated throughout the body. The heart is said to contract 4000 times in an hour; hence, as each ventricle contains one ounce of blood, there passes through the heart every hour 4000 ounces, or 350 pounds of blood. The whole mass of blood is about twenty-eight pounds, so that this quantity of blood passes through the heart thirteen or fourteen times in an hour, or about once in every four or five minutes. In the whale, ten or twelve gallons of blood are thrown out of the heart

ARTERY.-VEIN.-AIR.

at a stroke, with an immense velocity, through a tube of a foot diame. ter.

An ARTERY, or a pulsating blood-vessel, is a cylindrical canal conveying the blood immediately from the heart to all parts of the body for the purposes of nutrition, preservation of life, generation of heat, and the secretion of different fluids. The motion of the blood in the arteries is called the pulse; it corresponds with that of the heart. The pulse may be felt in various parts of the body, but the most usual place of feeling it is at the wrist. From seventy to eighty pulsations in a minute are commonly that number which in the adult subject is considered, as far as the pulse is concerned, to constitute health. In children, however, the pulse is much quicker than this; and in old persons slower. Wounds in arteries are always dangerous, and very frequently mortal'; hence the wisdom evinced in the structure of man: all the arteries are deeply imbedded in flesh, or other surrounding media, while the veins, a wound in which is comparatively unimportant, are plentifully scat tered on the surface of the body. The blood in the arteries is of a florid red color.

A VEIN is a blood-vessel which returns the blood from the various parts of the body to the heart. The veins do not pulsate; the blood flows through them very slowly, and is conveyed to the heart by the contractility of their coats, the pressure of the blood from the arteries, the action of the muscles, and respiration; and it is prevented from going backwards in the veins by valves, of which there are a great number. The blood in the veins is of a much darker red than that in the arteries.

Before we treat of the blood itself, it may be useful to know the component parts of atmospheric air, so essential as it is to the life of all warm blooded animals.

AIR was for many ages considered as a simple homogeneous fluid; and it was not till towards the end of the last century that it was found to be a compound body. Common air is composed chiefly of two gases, of which one, oxygen, forms of it 24 parts by weight, and the other, ni trogen, forms of it 76 parts; or about 21 parts of the former, and 79 of the latter by bulk. These proportions are found the same, in whatever part of the world the experiments are made, or from whatever height in the atmosphere the air is obtained. It ought however to be mentioned, that besides these ingredients, common air contains a very minute portion of carbonic acid gas, but that portion is in general so small as not indeed to be considered of any moment. Of the two portions of atmospheric air, the oxygen only supports animal life or combustion. Thus, if an animal be inclosed under a bell glass containing atmospherical air, it will live in it till all the oxygen is absorbed by its breathing, and then it instantly dies; the same takes place when a lighted candle is inclosed under similar circumstances; hence the necessity and importance of this fluid to animal existence. But although only about onefourth of atmospheric air can support life, it yet appears that such a mixture is more advantageous for animal life than oxygen alone; thus evincing the wisdom of that mixture found every where as atmospheric air. In what state of combination the two gases are, which constitute common air, is not exactly known; but we well know that a more