Before we begin the study of the Laws of Health, it is absolutely essential to know something of the human body, which is to be kept healthy.

Canon Kingsley, to whose suggestion the foundation of popular lectures of this kind is due, fully recognised this. He says, in his "Essay on Science and Health" (Health and Education, p. 13):-

" Why should not the experiment be tried, far and wide, of giving lectures on health, as supplementary to those lectures on animal physiology, which are, I am happy to say, becoming more and more common ? Why should not people be taught-they are already being taught at Birmingham-something about the tissues of the body, their structure and uses, the circulation of the blood, respiration, chemical changes in the air respired, amount breathed, digestion, nature of food, absorption, secretion, structure of the nervous system,-in fact, be taught something of how their own bodies are made, and how they wofk ? Teaching of this kind ought to, and will, in some more civilised age and country, be held a necessary element in the school course of every child, just as necessary as reading, writing, and arithmetic; for it is, after all, the most necessary branch of that 'technical education' of which we hear so much just now, namely, the or art, of keeping oneself alive and well.

"But we can hardly stop there. After we have taught the condition of health, we must teach also the condition of disease, of those diseases specially which tend to lessen wholesale the health of townsfolk exposed to an artificial mode of life. Surely young men and women should be taught something of the causes of zymotic disease, and of scrofula, consumption, rickets, dipsomania, cerebral derangement, and such like. They should be shown the practical value of pure air, pure water, unadulterated food, and dry dwellings. Is there one of them, man or woman, who would not be the safer and happier, and the more useful to his or her neighbours, if they had acquired some sound notions about those questions of drainage on which their own lives, and the lives of their children, may every day depend. I say-women as well as men. I should have said women rather than men; for it is the women who have the ordering of the household, the bringing up of the children; the women who bide at home, while the men are away, it may be at the other end of the earth."

We shall first consider the human body, the parts of which it is made, and the working of those parts.

The study of the parts or organs of which an organic being such as man is made, goes by the name of Anatomy; the study of the working of those parts or organs goes by the name of Physiology. We are about to study these two subjects together for the most part throughout the first few lectures, beginning from the simplest considerations.

The rough anatomy of a human being may be described as follows:-A human being consists of a head, trunk, and extremities or limbs.

The Head consists of two parts. One is called the cranium, the other the face. In the cranium is contained an organ, and a very important organ, the brain. In the face we find, in the first place, the beginning of the organs which deal with the food, which we call the digestive organs (that beginning is the mouth, and the things that are contained in the mouth), the beginning of the organs that have to do with breathing, which we call the respiratory organs- that beginning is the nose. We find, besides these, in the face, certain organs of special sense,-the organ of taste in the mouth, the organs of sight, and the organ of smell, placed in the position in which we should expect the organ of smell to be placed, nearly at the beginning of the organs of respiration^ nearly at the beginning of the tube through which air is taken into the body.

In the head we find also another pair of organs of special sense-the organs of hearing, which are situated in the walls of the cavity of the cranium.

The Trunk of human beings is roughly and ordinarily divided into two parts. The upper one is called the chest or thorax, and the lower one is called the belly or abdomen. We shall see hereafter that this is not merely a popular division, but that it is really a rational division.

The chest contains, in the first place, the heart, and in the second, the lungs-one on each side of the chest. It also contains the great blood-vessels connected with the heart and lungs, part of the windpipe which leads to the lungs, and the continuation of a tube, the gullet or swallow, which leads from the mouth to the rest of the digestive organs. The head is connected with the chest by the neck, through which the tubes just mentioned pass, viz., the windpipe, which is connected with the Mings, and which connects, the lungs with a cavity behind the mouth, into which the nostrils lead, and so with the nose; and the gullet or swallow, which is connected with the mouth, and passes down through the thorax into the next division of the trunk. In the lower division of the trunk, which we call the abdomen, there are contained, in the first place, the remainder of the organs of digestion, namely, the stomach, and the intestinal canal; the stomach being rather on the left hand side. On the right hand side of the abdomen is the liver. Besides these organs there is the spleen-an organ which is situated on the left hand side of the abdomen, to which the ancients attributed the property of causing anger, because they could find no other duty for it. Underneath the stomach, but situated rather behind it, is an organ we call the pancreas, which means all flesh; we eat the pancreas of the calf at table under the name of sweetbread. There are also two other important organs in the abdomen, one on each side, called the kidneys.

I have said already that the chest and abdomen are popular divisions of the trunk; but there is a very good reason for this-namely that in us, and in all animals of the class to which we belong, the mammalia-so called because they nourish their own young -the chest and the abdomen are divided from one another by a partition, which goes by the name of the diaphragm*

I have mentioned the chief separate contents of the chest and abdomen. Besides these there is a double chain of nerves with knots (which we call ganglia) upon them, running down through the thorax or chest, and through the abdomen, behind all these organs. This double chain of nerves goes by the name of the sympathetic nerves. But if you took a human being, and examined him right through, from front to back, in the chest or abdomen, you would also find a chain of bones running from the head downwards behind the cavities of the chest and abdomen; and behind that chain of bones, a tube running right down, and inside that tube, a white cord which we call the spinal cord; and if you looked farther, you would see that the spinal cord is continuous above with part of the brain, through a hole in the walls of the cranium.

The Extremities or limbs have no such cavities containing special organs as are in the head and trunk; they are solid throughout, except that they contain certain tubes. They, in fact, are made up of the same kind of structures as the walls of tjie body generally, and these structures we will now consider.

In the first place, the whole exterior of the body is covered by what we call the skin. In the skin there are two important layers: there is the skin proper, called the dermis, which is soft, moist, very sensitive, and supplied with a great deal of blood. It bleeds when it is cut. There is also a covering to the skin proper, which we call the epidermis, because it is upon the dermis, or outside of the skin proper. This is drier, not sensitive, not supplied with blood, and consists of horny scales which are continually falling off. All the surface of the body is covered with it. Wherever there is an opening from the interior of the body to the external air, the skin, as we understand it, ceases, and another substance, or rather something that we call by another name, takes its place. All the cavities of the body that communicate with the external air are lined by a kind of internal skin, which we call the mucous membrane. This internal skin resembles the external in that it has two important layers. It has a deep layer, which is soft, sensitive, well supplied with blood, and a superficial layer, which is moist, but otherwise not unlike the superficial layer of the skin itself, as it is insensitive and not supplied with blood; thus, at all the openings between the internal organs that communicate with the external air and the surface, this mucous membrane, which lines these internal organs, joins the skin, so that we see that the organs already described as in the body, and many that we have not mentioned, are, as it were, contained between these two skins.

The superficial layer of the mucous membrane is called the epithelium; so that in the skin we have the dermis or true skin, and the epidermis, which is sometimes called the scarf skin; and in the mucous membrane a deep layer, and a superficial layer called the epithelium. Underneath the skin of the body we find, in the first place, a more or less thick layer of fat, which is thicker in certain parts of the body than in others, and beneath that a number of structures that we call muscles or flesh.

We find this whether we take the extremities, or the walls of the body anywhere, and we find besides this a number of tubes containing blood, called blood-vessels, in all parts of the body below the epidermis or below the epithelium, and other tubes not containing blood, but a nearly colourless fluid, which, from its resemblance to water, is called lymph. These tubes go by the name of lymphatic ducts. Besides them we find white cords in almost all parts of the body, more or less directly connected with the brain or the spinal cord, which we call nerves. These are the structures that we find in the limbs, and also wherever we examine the walls of the body.

Such is a very brief outline of the more important organs of the body, and the way in which they are put together.

We will now pass on to consider parts of the body more particularly, and will begin with the bones. In the young human body there are more them two hundred separate bones, but some of these grow together in the adult, so that several form one bone.