"Let every thing that hath breath praise the Lord. Praise ye the Lord."-PSALM CL.

carbon, by which a gentle heat is diffused throughout the system. It is for this purpose that fresh air is so constantly

necessary.

But other exchanges take place. The blood, in addition to oxygen and carbon, contains hydrogen and nitrogen. But it contains its four elements in various forms of combination, producing the following materials for the use of the body of 1,000 parts of blood, about 779 are water; 141 are red globules; 69 are albumen; 3 are fibrin; 2 are fatty matter; 6 are various salts.

:

Albumen and fibrin are a kind of flesh imperfectly formed, and probably are chiefly used in repairing the muscles. The red corpuscles contain the oxygen which goes to combine with the superabundant carbon, and develope heat; the fatty matters probably repair the fatty tissues, and glands that are of a fatty nature; and the various salts contribute to the bones, and to the chemical properties of those secretions which are formed by the glands, &c., while the great proportion of water is employed in cleansing, softening, and cooling the whole, or the living edifice, and it is the medium through which all the nutrition of the body is distributed.

900. Why do we feel the pulse beat?

Because every time that the heart contracts it send a fresh supply of blood to the blood-vessels, and the motion thus imparted creates a general pulsation throughout the system: but it is more distinctly perceived at the pulse, because there a rather large artery lies near to the surface.

901. What becomes of the matter collected by the blood in the course of its circulation?

We have already explained that carbon is thrown off from the lungs in the form of carbonic acid gas. But there are many other matters to be separated from the venous blood, and its putrification is assisted by the action of the liver, which is supplied with a large vein, called the portal vein, which conveys into the substance of the liver, a large proportion of the venous blood, from which that organ draws off those matters which form the bile, and other matters which are transmitted with the bile to the bowels. The liver and

"Thy hands have made me and fashioned me: give me understanding, that I may learn thy commandments."-PSALM CXIX.

the lungs, therefore, are the great purifiers of the venous blood. But there are also smaller organs that assist in the same work.

Fig. 53.-SHOWING THE DISTRIBUTION OF BLOOD THROUGH BRANCHES OF A. The aorta.

THE AORTA.

B. Branches given off for the aorta to supply one portion of the intestines. C. Branches given off by the aorta to supply other portions of the intestines. A complete communication may be traced between these vessels from the origin of one to that of the other.

D. The pancreas, or sweetbread, a large gland that forms the pancreatic juice, which it pours in through the duct. See Fig. 50.

EE E. The large intestines, forming the termination of the alimentary canal.

CHAPTER XLIV.

902. Why when we cut our flesh does it heal?

"And God said, Let us make man in our own image, after our likeness; and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing."-GEN. I.

Because the blood coagulates over the cut, and throws out a kind of lymph, which forms an incipient flesh, and excludes the air while the blood-vessels are engaged in repairing the part.

903. Why, since all the substance of the body undergoes change, do we preserve the same features throughout our lives?

Because our substance changes in the minutest atoms; and each separate atom has a life of itself, the maintenance of which preserves the unity and permanence of the whole.

904. Why do moles upon the skin continue permanent, while bruises and wounds disappear?

Because moles are themselves organised formations, and repair themselves just as any other part of the body does. But bruises and wounds are the result of accidental disturbances, which in course of time become removed.

905. Why do the marks of deep cuts sometimes remain?

If the cut is so deep and serious as to destroy the system of vessels which supply and repair the part, then it is evident that they cannot work so perfectly as when in their sound condition. Their functions are, therefore, interfered with, and instead of having flesh uniform with the other parts of the system, there results a scar, or a wound imperfectly repaired.

906. Why when we hold our hands against a candlelight do we perceive a beautiful crimson colour?

Because the fluids and vessels of the body are in some degree transparent, and the thin textures of the sides of the fingers allows the light to pass, and shows the beautiful crimson colour of the blood.

If the web of a frog's foot be brought in the field of a good microscope, and set against a strong light, the blood may be seen in circulation, with the most wonderful effect. Each vessel, and every globule of blood, can be seen most distinctly, and the junction of the arteries and veins can be clearly traced. The ittle boats of nutrition may be seen chasing each other in rapid succession, and when the animal exerts itself to escape, the flow of the blood increases; and not unfrequently, under these circumstances of agitation, have we seen two or three blood discs struggling together to enter a vessel that was too small for them. Again and again they have endeavoured to find a passage, until one of them happening to slip forward, got away, followed by the others!

"Know ye that the Lord he is God: it is he that hath made us, and not we ourselves: we are his people, and the sheep of his pasture."-PSALM C

907. Why does the flesh underneath the nails look red? Because the transparent texture of the nails enables us to see the colour of the vascular structure that lies underneath the skin. Vascular.-Full of vessels. In this instance, full of capillary blood-vessels. 908. Why have we nails at our fingers' ends?

Because they give firmness to the touch, and enable us to apply the extremities of the fingers to many useful purposes for which they would otherwise be unfitted. They enable us to press the tips of the fingers, where the highest degree of sensitiveness prevails, so as to bring the largest amount of nervous perception into the sense of touch.

909. Why do white spots occur upon the nails?

Because the vascular surface underneath is attached to the horny texture of the nail; but by knocks and other causes, the nail sometimes separates in small patches from the membrane below, and becomes dry and opaque.

910. Why is there a circular line of whitish colour at the root of the nail ?

Because there the nail is newly formed by the vascular substance out of which it grows, and has not yet assumed its proper horny and transparent nature.

911. Why is the eye-ball white?

Because the blood-vessels that supply its surface are so very fine that they do not admit the red corpuscles of the blood.

912. Why does the eye-ball sometimes become blood-shot? Because, under exciting causes of inflammation, the blood-vessels become distended, and the red corpuscles enter, producing a network of red blood-vessels across the white surface of the eye.

913. Why are the lips red?

Because the lips are formed of the mucous membrane that lines the body internally, and covers the surface of most of the internal parts. This membrane contains a great number of minute red vessels, which give softness and moisture to the surface. A very beautiful

"Hast thou not known, hast thou not heard, that the everlasting God, the Lord, the Creator of the ends of the earth, fainteth not, neither is weary? there is no searching of his understanding."-ISAIAH XL.

illustration of the softness, moisture, and delicate colour of the mucous membrane is afforded by turning up and examining the under surface of the upper eye-lid.

914. Why do delicate persons look pale and languid ? Because, generally from the want of exercise and fresh air, their blood is deficient of the healthy proportion of red corpuscles.

915. Why does exercise and fresh air impart to healthy persons a red and fresh appearance?

Because the redness of the blood is due to the amount of oxygen. which it contains, and air and exercise oxygenise the blood, and diffuse it throughout the system.

916. How is the blood propelled through the arteries?

By the very powerful contraction (and alternate dilation) of the thick muscles of the heart, assisted also by the muscular cords of the blood-vessels themselves, and in many instances by the compression of the muscles in which the arteries lie embedded.

917. Why are the capillary arteries capable of receiving the great quantity of blood sent out through the larger vessels?

Because the capillary vessels are so numerous, that though they are infinitely smaller, they are capable of receiving in their minute tubes the whole of the quantity of blood transmitted to them through the larger vessels.

918. Why, when we sit with our legs crossed, do we see the foot that is raised move at regular intervals?

Because the pressure upon the muscles of the leg retards the progress of the blood until it forces itself through the compressed vessels, and thereby imparts a pulsation which moves the leg and foot.

919. Why are capillary blood-vessels found in every part of the system? ·

Because it is through these small vessels alone that the substances of the body are renewed and changed. Even the larger blood