noise of the circulation of the blood. It is the voice of all the vital processes together-the tearing down and building up processes that are always going forward in every living body from conception to death.

We have never seen a finer description of the circulation of the blood than that by Mrs. Hack. She compares the arrangement of the blood-vessels in the human body to the manner in which the water-pipes of a great city are laid to supply the people with water. She speaks of the heart as the engine which forces the water from its natural fountains into the distributing pipes, which run out in different directions, and from these smaller pipes branch out into streets and alleys, while still smaller ones issue from them, and convey the water into private houses. So far the resemblance is complete. These water-pipes represent the arteries which carry the blood from the heart to the extremities of the body; but in the human body another contrivance was necessary. The citizens of a city may use the water or waste it as they please; but the precious fluid conveyed by the arteries to the ends of the fingers must be returned to the heart; for on its unceasing circulation our health depends.

"In order to effect this purpose, another set of pipes is prepared, called veins, which, joining the extremities of the arteries, receive the blood from them, and carry it back again to the heart. The veins present the same general appearance as the arteries; but as it is the office of the arteries to distribute the blood, so it is that of the veins to collect it. Through them it flows back to the heart in a manner just the reverse of that in which it sets out; the minute veins unite in larger branches, the larger branches in still larger trunks, till the collected blood is at length poured into the heart through one opening.

"The engine that works this curious machinery is the heart. The heart is composed of four cavities. Like other muscles, it has the power of contracting; and when it contracts, the sides of its cavities are squeezed together, so as to force out any fluid the heart may at that moment contain. This purpose being effected, the fibres relax, the heart once more becomes hollow, and as it dilates, the blood pours into the cavities from the large veins which

bring it back to the heart. The next contraction forces the blood into the arteries, the quantity thus impelled being always equal to that which has just been received; and thus this wonderful organ goes on, alternately contracting and dilating itself, four thousand times an hour. Month after month, year after year, it goes on without weariness or interruption, conveying renewed strength to every part of the body. The two largest cavities of the heart, which send out the blood to the arteries, are called ventricles; the two smallest, which receive it from the veins, auricles. All the arteries are furnished with valves that play easily forward, but admit not the blood to return to the heart.

"In all this there is abundant evidence of wise contrivance. The blood, in going out from the heart, is continually passing from wide tubes into those which are narrower; in coming back, it passes from narrow vessels into wider; consequently presses the sides of the arteries with greater force than it acts against the coats of the veins. To prevent any danger from this difference of pressure, the arteries are formed of much tougher and stronger materials than the veins. This is one difference between the two; there is another still more strikingly illustrative of the care of the Great Artificer. As a wound in the arteries, through which the blood passes with such force from the heart, would be more dangerous than a wound in the veins, the arteries are defended, not only by their stronger texture, but by their more sheltered situation. They are deeply buried among the muscles, or they creep along grooves made for them in the bones. The under side of the ribs is sloped and furrowed, to allow these important tubes to pass along in safety; and in the fingers, which are liable to so many casualties, the bones are hollowed out in the inside like a scoop. Along this channel the artery runs in such security, that you might cut your finger across to the bone without doing it any injury."

In case of a wound, however the blood flowing through the orifice tends to coagulate and adhere to the edges of the wounded part, forming at last a complete scale and stopping the flow. This arrangement of nature is the only thing which prevents one bleeding to death after injury to the blood-vessels.

THE PROCESS OF DIGESTION.

Physical life is a series of changes which begin with the dawn of existence and end in death. These changes are continually taking place, and consist of a removal of old, worn-out particles, and an incessant supply of new ones. It is thought that the entire body thus becomes radically changed once in every seven years. If a person lives to be seventy years old, he has then been in possession, not of ten different bodies, but of one body substantially renewed ten times. So gradual and secret are these changes that the person has no consciousness of them. They are produced by the habitual introduction of new matter in the animal economy, the nutrition of which is assimilated by the organs and sustains the even flow of life.

The visible process by which life is sustained is that of eating and drinking. The stomach is the organ which receives our food, and is described as "a highly irritable and sensitive organ, having numerous muscular fibers entering into its composition, and being plentifully supplied with nerves. From its internal surface there is a fluid constantly secreting, called the gastric juice, which has the peculiar properties of dissolving and attenuating the food before it passes into the intestines."

Situated near the stomach is the liver which secretes a dark-colored fluid, called bile, the precise purpose of which is scarcely known, save that it converts the food into chyle and, pouring into the intestines, stimulates them to proper action. It is estimated that two or three pounds of bile are secreted every day, the flow of which into the intestines is essential to life and health.

Digestion is a complicated process. The first step is mastication which is accomplished in the mouth. The teeth grind the food, and the saliva, about three pounds of which are secreted daily, moistens it. The food, thus reduced, is carried by muscular action down the oesophagus into the stomach, where, as we have noted, the gastric juice flows upon it and excites the muscles of the stomach into action, something like a churning motion, which thoroughly mixes the gastric juice with the food. As the food, in this condition, passes out of the stomach, it receives the secretions of the

pancreas and the liver, enters the intestines, where digestion is completed, and is finally expelled from the system. During the whole of this process, the health-giving properties of the food are taken up by the absorbents and carried into the circulation. When the digestion is imperfect, disease is the result. The trouble generally begins with ill-performed mastication, and for this we ourselves are responsible. The state of the mind, as of fear, worry, and the like, is said to operate unfavorably upon digestion.

SENSE AND SENSATION.

We must distinguish between sense and sensation. It is clear that there is a great variety of sensation; but this does not imply a corresponding variety in our senses. The same organ may furnish several sensations but be the avenue of only a single sense. The eye is the organ of sight, but it may also give us a sensation of pain. The tongue is the organ of taste, but by applying it to an object we may receive through it ideas of form, solidity, etc. The brain, spinal marrow, and nerves alone are supposed to constitute the sensation part of the human system; all the other parts consisting of matter entirely insensible, save as they are interpenetrated by nerve branches. Some think, however, that the bones send sensations to the brain. We know, at least, that when fractured or diseased they are deeply sensible and manage somehow to let us know it. Dr. Geo. M. Beard says that the muscles are all endowed with a sense of feeling, by the distribution of the nervous fiber everywhere throughout their substance. This is necessary to their office. As agents of voluntary motion, they must be capable of receiving and obeying the commands of the will; and they are so. Hence, the mind no sooner wills an act than the command flies along the nerve to the part to be moved, and the action is instantly performed.

The nerves convey messages from and to the brain. If you injure your little toe the fact is communicated as quick as a flash of lightning through the whole length of your body to the brain cells and the mind.

If your hands are cold the fact is telegraphed to the brain. The

nerves are the telegraph lines, and the messages they transmit in a single day are numberless.

Sensibility is the general property of every animal organism, and is specialised in proportion as the organism is special and complex in structure. Although every animal must feel, it does not follow that every animal must have every kind of feeling. The mollusk feels, in its way, but it is doubtful whether it can experience pain. Its sense of sight is probably little more than a simple discrimination of light from darkness. The cat hears sounds, but does not seem to be very discriminating in its ideas of harmony. Among men there are those who cannot distinguish colors, or odors, or melodies, so defective in them do these special senses appear to be. Some are exquisitely sensative to pain or tickling; others much less so, the specialties of the general sensibility depending on the specialties of the nervous system and the organs of sense.

It is commonly said that we have five senses, but there may be more. Hutcheson affirms that this division is ridiculously imperfect. He thinks such experiences as hunger and thirst, weariness and sickness, can be reduced to none of the five external senses; or if they are reduced to feelings, they are perceptions as different from the other ideas of touch-such as cold, heat, hardness, softness as the ideas of taste and smell.

Dr. Dio Lewis speaks of the "Sense of Direction." This, he says, is possessed in but slight degree by men who live in cities, but men who live a wild life on the plains or in the forests often have it in a high degree. There are many animals whose "sense of direction" is wonderful. A pigeon, of what is known as the homing" variety, taken from New York to any distant city in a box, within a car, and released, will rise in the air, make a circle or two, and immediately commence, with the most unerring certainty, a bee-line for his little box in New York. A cat, put in a close bag, and taken ten or twenty miles from her house at night, will appear in her former haunts early next morning. This "sense of direction" is common among animals, and is as unerring as the sense of sight. Man has it, but not to such extent, his reason being to him a better guide.

The five special senses-sometimes called sense-sensations—are