you see the cause of that variety of colour which exists among the different families of the human race. The third skin, called the CORIUM, is the true skin, of which, in inferior animals, leather is made; and which, when boiled in water, is converted into glue. This skin seems to be composed almost entirely of blood-vessels and nerves. The universal and equal redness of the skin in a blushing face, is a proof of its being filled with blood. This skin is the seat of sensation and of touch, and the instrument of perspiration and absorption, the right condition or disturbance of which, is a most powerful agent in the preservation or injury of the health. It is affirmed by some, that "during twenty-four hours, the skin discharges two pints or more fluid, by invisible perspiration; and a much greater amount when, by exercise or heat, it sensibly bedews the surface. It is said, indeed, that a robust man, engaged in hard labour, and exposed to intense heat [as the glass-blower, sugarbaker, &c.], has been known to lose five pounds weight in the course of an hour."*

If persons in general were aware of the important offices which the skin sustains, and how necessary it is, for the proper discharge of its functions, that the pores should be kept free from obstruction, for the skin is extremely porous, or full of holes, there would be much more attention paid to the habitual and thorough cleansing of the body, and the frequent and regular change of apparel; thereby preventing fevers, inflammations, &c. "Every one knows that the skin perspires, and that checked perspiration is a powerful cause of disease and of death. When the body is overheated by exercise in warm weather, a copious sweat soon breaks out; which, by evaporating, and so carrying off the superfluous heat, produces an agreeable feeling of coolness and refreshment. . . . . But in the ordinary state, the skin is constantly giving out a large quantity of waste materials by what is called insensible perspiration; a process which is of great importance to the preservation of health. . . There is a close sympathy between the skin and the stomach and bowels; and most of the obstinate eruptions which appear on the face and the rest of the surface, owe their origin to disorders of the digestive organs, and are most successfully cured by treatment directed to the internal disease.

So perfect is the sympathy between these two distinct parts or organs, that when the skin is primarily affected, the "The Philosophy of Life, Health, and Disease," by C. Searle, M.D., p. 23.

stomach becomes secondarily so, and vice versa; so that a sudden check to the heat of the body as often brings disease of some internal organ, as if the cause were applied directly to the organ itself."

IX. There is another substance of the human body which we must not pass over; namely,

THE FAT.

In most parts of the body, the fat lies immediately under the skin. It is generally white or yellowish. There is in most persons a small quantity of fat intermixed with the muscles; and in some persons a great deal of it. A small portion only of fat is necessary to health, and when found, as is frequently the case, in unusually large quantities, in man, or in other animals, it rather indicates disease. The fat affords, by its power of resisting the passage of heat, a warm covering to animals that are destined to live in cold climates; and it is in these that we find it accumulated to the largest amount. Animals which inhabit tropical or hot climates, possess very little fat. The fat, being deposited when nourishment is abundant, serves as a store which may be taken back by the blood-vessels into the system, and made use of in time of need. In diseases which prevent the reception of food, the fat in the body rapidly diminishes. This is the case, too, with those animals that hybernate, or sleep during the winter. These animals usually accumulate a considerable amount of fat in the autumn, and are observed to come forth, on the return of spring, in a very lean condition.

The fat is supposed to be insensible, unconscious of pain, as none of the sensitive nerves pervade it. Hence it is used in the Holy Scriptures as a figure denoting moral insensibility,want of feeling. The charge brought against Israel was,"This people's heart is waxed fat."

X. I close with a few words on

THE NAILS AND HAIR.

1. The NAILS are a horny substance growing at the end of

* Combe's "Principles of Physiology,” pp. 50. 59.

the human fingers and toes. They belong to the epidermis, or outer skin, and separate with it; and like it, they have neither blood-vessels nor nerves, and may be cut or bruised without pain. In the fingers they increase the power of apprehension, being useful in laying hold of and retaining objects. We cannot say of what use are the nails of the feet, except as a slight protection to the toes. In a delicate, well-formed foot, however, they may be considered as an ornament. Were the human foot left at liberty as it was among the ancient Jews, Greeks, and Romans, who wore sandals only, it would be much more comely in appearance than it now is, cramped by tight boots and shoes, the prolific source of that malady which frequently proves a too sensitive and accurate barometer, and furnishes ample employment and cash for many pretending chiropodists.

2. HAIR, in greater or less quantity, is found on all parts of the body, excepting the palms of the hands, and the soles of the feet; but more particularly it abounds upon the head. Each hair is a hollow tube supposed to contain some kind of matter. Hairs have their origin in little roots or bulbs which are situated in the lower or true skin. Neither nerves nor blood-vessels pass into the substance of the hair. There is an evident relation between the colour of the hair and the shade of the skin. Dark-skinned individuals have generally dark hair; while the hair of fair persons is usually of a light colour. The hair, especially that of the head, and of the eyebrows and eyelashes, serves in general for the ornament, warmth, and protection of the different parts of the body. In many instances, the hair of the head loses its natural colour by age, and turns grey or perfectly white: and "the hoary head is a crown of glory, when it is found in the way of righteousness."

SECOND LECTURE.

THE present Course of Lectures is on MAN. The constituent and essential parts of man are two,-body and soul. The one was made out of the dust; the other was "breathed into him.” The body is formed with the greatest precision and exactness; every bone, muscle, vein, artery,-yea, the least fibre, in its proper place; all in just proportion and symmetry, in subserviency to the will of each other, and for the good of the whole. It is also made erect, to distinguish it from the four-footed animals, which look downward to the earth. Man was made to look upward to the heavens, to contemplate them, and the glory of God displayed in them; to look up to God, to worship and adore him. It is this erect posture which gives to the aspect of man that dignity becoming his high place in the creation.

"Os homini sublime dedit: cœlumque tueri

Jussit, et erectos ad sidera tollere vultus."-OVID.

By the adaptation of an erect structure, also, his hands are left disengaged, and ready for the numerous operations to which he is inclined by his judgment, or urged by his wants.

"The general stature of the human being is between five and six feet. The infancy of man is longer than that of other animals he does not attain his full growth till he is upwards of twenty years of age. For other thirty years, if not cut off by disease, he is in the prime of his strength. Twenty years more constitute elderliness; and if he survive seventy years in all, he is said to reach old age.'

The subjects of my last Lecture were-the Human Skeleton;-the Skull;-the Vertebræ ;-the Bones, including the Ribs, the Collar-bones, the Shoulder-blade, the Arm and Leg bones; the bones of the Hand and Foot; and the Teeth; adding a few words on the Joints. Then followed the Muscles and Tendons; the Cartilages; the Nerves; the Skin; and a few brief observations on the Fat; the Nails; and the Hair.

*Chambers's "Introduction to the Sciences," p. 120.

D

We now proceed to notice the more internal parts of the human frame; beginning with

1. THE BRAIN AND SPINAL MARROW.

The structure of the BRAIN is so complicated, that less is known of its true nature than of that of almost any other organ. It is that soft and whitish mass of pulp enclosed in the skull, from which the nerves and spinal marrow proceed. It is said to be furnished with a three-fold greater proportion of blood than any other organ. This mass is divided into two halves, termed hemispheres, resembling a boiled egg without the shell, cut down lengthwise. Each hemisphere is again sub-divided into a front, middle, and back lobe or lump. "The white substance of the brain is usually described by two names; the upper and front part, which is by far the largest, is termed the cerebrum; and the lower portion is named cerebellum, or little brain; both of which, being united together, are closely and firmly enveloped in three distinct membranes, or coats; and the whole weight of which, in an ordinary sized man, is about three pounds."* The entire brain is again further separated into numerous small lumps, termed convolutions, which run in different directions, and may be compared to a mass of white soft sausages intertwined and gently compressed together. In the cerebellum there is what is called the arbor vita, or tree of life; which has all the appearance of a beautiful display of the branches and twigs and leaves of a tree. "The brain of the human being is supposed, by some, to attain its full weight and size at seven years of age; by others it is supposed to increase in weight till the age of fourteen. Idiots' brains are usually very small, weighing only about twenty or twenty-five ounces. But the size of the brain bears no constant relation to the genius of the person." It is a striking fact, however, that almost all those persons who have been eminent for the amount of their acquirements, or for the influence they have obtained by their talents for command over their fellow-men, have had large brains; this was the case, for example, with Newton, Cuvier, and Napoleon. The brain contains seven cavities, or hollow places. In their natural size, these are exceedingly small; yet by disease they are sometimes enlarged enormously, and being filled with a watery fluid, produce that dis*Chambers's "Introduction to the Sciences," p. 120. + Knox's "Manual of Anatomy,' p. 547.