of the bones of the child being consolidated into one bone during its approach to adult years. For the convenience of study, it is usual to speak of the skeleton in three separate parts, viz., the HEAD, the TRUNK, and the EXTREMITIES. 1. In the head alone there are fifty-nine separate bones, which may be thus classified: In the skull proper 8 bones. 2. In the trunk will be found 54 bones, as follows: In the backbone 24 bones. In the chest In the pelvis 3. In the extremities there are 124 distinct extremities, and 60 in the lower extremities. follows, viz.: In the shoulders and arms In the wrists 25 bones. 5 bones. bones, 64 in the upper They will be found as 10 bones. In the hands In the fingers and thumbs Making for the upper extremities While those of the lower extremities are found thus: In the legs 16 bones. 10 bones. 28 bones. 64 bones. 8 bones. 14 bones. 10 bones. 28 bones. 60 bones. In the ankles In the foot In the toes Being in the lower extremities Thus far it will be perceived that we have only contemplated the solid frame work upon which the other portions of the body are constructed, and yet of these "dry bones" we might find topics of reflection and admiration so numerous and extensive, that our time is too limited even to indicate. Suffice it to say, that of this large number of separate bones in the body, there are many individual bones, the composition, form, structure, connections, and uses of which would furnish an ample theme for an entire lecture. And of the bones in general, of the shape and firmness they give to the body, of the support they give to its various parts, of the defense they furnish for the vital organs, of the levers they provide for the muscles to act upon, we cannot dwell for a moment, full of interest as are these several topics. Next to the bones, and closely attached to them, are found certain bands or straps, which are called LIGAMENTS, and by these the bones are firmly connected together, constituting the hinges, or other mechan. ism, by which the ends of the several bones are connected with each other, and the multiplied joints of the body are constructed. And for the facility of motion, and to guard against the effects of friction, upon the surfaces of the ligaments, covering the ends of each bone entering into the form of a joint, an oily fluid is poured out by vessels constructed for the purpose, which renders the motions of the joints easy in the performance of all the variety of action to which any part of the body may be subjected. This single topic of the ligaments and joints opens before us a wide field of instruction: their number, variety, offices, and durability. But we must dismiss it with barely remarking, in the language of Dr. Paley, that "a limb shall swing upon its hinge, or play in its socket, many hundred times in an hour, for sixty years together, without any diminution of agility." Where is to be found on earth a piece of mechanism the hinges or joints of which can be thus worn, without ever being out of repair or of what material could joints be constructed, in any machine of human invention, which would wear so long? . We now pass to the consideration of the instruments of motion in human organization, which are called MUSCLES. There are found in the body five hundred and twenty-seven muscles; two hundred and fiftyseven of them are double, being found in pairs: and thirteen of them are single. In common language, the muscles of the body are called by the general name of flesh: but notwithstanding the large number of the muscles included in the fleshy portions of the body, each of them is found, on examination, not only distinct from every other, but made up of innumerable threads or fibres, invariably formed with reference to the motion they are destined to perform. They vary essentially in size, in shape, in length, and structure; and every muscle is inclosed in a sheath, like those which are seen to divide the inside layers of an orange, while each minute fibre or muscle is similarly enveloped, and over all the muscles is a stronger sheath covering the entire limb, or other division of the structure, which several sheaths not only serve to keep the action of one muscle or fibre from interfering with that of another, but, by their elasticity, they contract or expand with every use made of the muscles, and give support and security to the whole. These muscles are the instruments of motion, and are either voluntary or involuntary. The former are under the control of the will, but the latter act without the will, and in despite of the will being exerted to the contrary. To produce the contraction or relaxation of any voluntary muscle, or any limb, including the whole of its muscles, we have only to will it, and simultaneously the muscles obey the mandate. The muscular fibres of the stomach, the heart, and those concerned in respiration, as well as those of the internal ear, are examples of involuntary motion, performed nevertheless by muscles. Each muscle terminates in a hard white cord, called a tendon or sinew, which varies in shape and size according to the office it is to perform, and this tendon passes through a sheath, within which an oily fluid is secreted analogous to that found in the joints, to obviate friction, and permit the tendon to glide easily. It is to the tendons we are indebted for the symmetry of form, both in the body and limbs, the result of their beautiful structure and diminished size; the large fleshy muscles of the arm for example, having long, slender, and silvery tendons or cords passing down upon the fingers, and occupying very little space. Every muscle, with few exceptions, has an antagonist muscle; one bends the limb, the other extends it: one relaxes, while the opposite one contracts. It is by this mechanism that we have so much rapidity of motion in different and opposite directions. The irritability or contractility of muscular fibres remains, in numerous instances, after death for a considerable time, so that it is found that they will contract on the application of galvanism, or any powerful stimulant, and sometimes spontaneously. Hence the heart, and other muscular structure of reptiles, will move on being pricked with a needle, after they have been removed from the body for hours. Some have thence alleged that they possess a sensibility independent of the brain and nerves: but it only shows that the nervous influence communicated to the fibres during life has not been exhausted, but continues for a longer or shorter time after death. It is the interruption or loss of this nervous power or influence which causes cramps, spasms, and painful contractions of the muscles, which are found to be beyond the control of the will: and this happens from fatigue. It has been remarked as a subject of astonishment, that the muscles never become weary, even in the cases just named. In the simple act of breathing, not less than a hundred of these muscles are constantly acting, whether we are in motion or at rest, sleeping or waking, and this muscular motion is kept up from the moment of birth often for nearly a century, during all which time these one hundred muscles perform, on an average, twenty inspirations and expirations every minute. The muscular fibres of the heart, during the same protracted period, are in perpetual motion, propelling the blood into the arteries on the like average sixty times in a minute. And so also of numerous other examples in the body. Dr. Paley on this subject thus expresses himself: "Breathing with ease is a blessing of every moment, yet of all others we possess it with the least consciousness, though a hundred of our muscles are ever actively employed in the process. A man in an asthma is the only one who knows how to estimate it." The muscles, though composed of so slender threads or fibres, are so compacted together by their sheaths, that they possess extraordinary power, as has been demonstrated by a variety of experiments and calculations. The heart is estimated to exert a force of above a thousand pounds in propelling the blood out of the arteries into the veins. A man weighing one hundred and fifty pounds, in leaping two feet into the air, exerts a force two thousand times greater, equal to three hundred thousand pounds. If the teeth be employed in lifting a weight of two hundred pounds, attached to a rope, as is sometimes done, the muscles of the temple, by which chewing is ordinarily performed, must exert a force equal to fifteen thousand pounds' weight. But I forbear to enlarge here, though very much more should be said in justice to this important department, if the occasion did not forbid any degree of amplification. Having commenced with the bones, and next contemplated the muscles, your attention is now directed to the SKIN, with which the entire surface of the body is covered. Between the muscles and the skin is deposited a layer of spongy, fatty structure, which is called cellular substance, which, though greatly increased in fat and corpulent persons, is found universally to greater or less extent, even during great emaciation. Next to this lies the true skin, enveloping the whole, This and it is made up of vessels and nerves, to such an extent that it may be said to be a membrane interwoven with these, since all the nerves, arteries, and veins of the body, are found to terminate here. true skin is white in all the races of men, the differences in color arising from another coat next to be noticed. On the upper surface of the true skin it is smooth and delicate, but its texture is much looser beneath, where it adheres to the cellular substance. Directly over the true skin, a layer of thin coloring matter, paint, or pigment, is found, spread all over the external surface of the body, upon the true skin. I say the external surface, because at the lips, margin of the eyes, nostrils, &c., this structure ceases, and hence the change of color. Its red appearance depends upon the blood seen through the true skin within its hair drawn vessels, for on dissecting it off it is found white and semi-transparent. This pigment is called the rete mucosum, or mucus net-work, and in the negro it is black, in the Indian red or copper-colored, in the Spaniard yellowish, and white in the Caucasian, or white variety of our species. This mucous paste or paint is constantly poured out upon the skin, and is supposed to protect its irritable surface from the effects of light, air, and heat. These agents undoubtedly exert an action upon this net-work, which dries, becomes hard and insensible, and is constantly reproduced. Over this net-work, or rete mucosum, is found the scarf-skin, the external coat of all, and is seen to be raised by the action of blisters. It is semi-transparent; hence the color of the pigment beneath is seen through it. It is totally insensible, rough, and varies in thickness. In the palms of the hands, and the soles of the feet, we have an example of its great thickening, which serves as a defense for the delicate nervous structure in those situations. The nails are supposed by many to be the product of this thickened scarf-skin. This external coat of the skin is constantly worn off, and as constantly renewed; which has led to the opinion that it is nothing more than the rete mucosum thrown off from its surface. It is well known that the palms of the negro's hands are not perfectly black, but, on the contrary, often of a clear white. This is explained by the scarf-skin and rete mucosum having been worn off, and the true skin being no longer covered by its pigment. This is known to be the case in wounds, and especially burns, occurring on any part of a negro's body; the scar is ever after white. It results from the destruction of this net-work by the injury, and the subsequent closure of the ducts in the part, which before poured out the pigment. Similar results are observed in the negro from certain diseases of the skin, by which a great portion of the body often becomes white, and still oftener produces large white spots upon the former black skin. An argument has been founded on this fact, by a recent sect of would-be philosophers, to prove that black was the original color of the skin, and that the whites are a degenerate race, the color being the effect of disease. If this doctrine did not smack of transcendentalism, amalgamation of the races would be a desideratum for the sake of getting rid of a diseased skin, in posterity at least, by improving the breed. Attached to the skin, as, for example, covering the head, we find the HAIR growing from its surface. Each particular hair is found grow ing from a bulbous root, imbedded in the skin and containing a peculiar fluid secreted for its nutrition. Thus far we have noticed the bones, the muscles, and the skin, and yet we have but entered upon the intricacies and mysteries of human organization. Such has been the extensive and accurate knowledge of the body, discovered and demonstrated by the researches of modern anatomy, that what was formerly the utmost extent of acquaintance with human structure, is now considered justly as but the threshold of this vast subject. Indeed, it would seem that in the time of the prophet Ezekiel nothing more of anatomy was known than that fragment we have already considered. For in his vision of the valley of dry bones he only clothed the bones with sinews and flesh, by which he meant the tendons and muscles, and then covering them with skin, he thus completed the organization of structure, into which he sought only the breath of life. It is rational to conclude that any farther reference to human anatomy, in this vision, would have been unintelligible to the people, and possibly to Ezekiel himself, for had it been otherwise, the divine afflatus would have enumerated other parts of human structure. We are now prepared to understand that, had his vision been literally realized, the breath of life would have availed nothing without the lungs and breathing apparatus, nor without the heart, blood vessels, nerves, glands, viscera, and other important and necessary constituents of the organization of the human body, both solids and fluids; and we therefore, after this digression, proceed to our task, introducing next to your attention the heart and circulation of the blood. And, first, of the HEART. I shall purposely abstain from any of the illustrations drawn from comparative anatomy, by writers upon this topic, as unintelligible to a popular audience, and out of place here. To speak accurately, however, it is necessary to say that man has two hearts, united, it is true, into one, constituting a compound engine consisting of two forcing pumps. The same is true of quadrupeds, birds, and all warm blooded animals. These two hearts, the right and left, act and rest alternately, and each of them has two cavities, an auricle and a ventricle, communicating with each other by an opening about an inch wide, on the margin of which is suspended a valve or gate, which prevents the regurgitation of the blood at each pulsation. And a multitude of little cords cross and recross these cavities, and serve to aid their contractions, as well as to prevent them from being over distended. These are what are vulgarly called heart-strings, but they do not break in the act of dying, as is commonly supposed. A tough elastic bag, case, or sac, also surrounds the heart; and lastly, this organ is still farther guarded by the ribs and muscles, constituting, with the breast bone, the anterior wall of the chest, while, posteriorly, the spinal column and ribs, with their muscles, protect it yet more securely. It lies between the lungs, in a triangular space, suspended by its own vessels, and at liberty to swing from the top of the chest, conformably to the motions of the body. Its shape is an irregular cone, and not at all like the representations upon playing cards, and sometimes in books. It is a hollow muscle, being made up of muscular fibres possessing inherent contractility, as some allege; but this |