Physiology and Hygiene for Secondary Schools

Chapter I - Introduction

To derive strength equal to the daily task; to experience the advantages of health and avoid the pain, inconvenience, and danger of disease; to live out contentedly and usefully the natural span of life: these are problems that concern all people. They are, however, but different phases of one great problem--the problem of properly managing or caring for the body. To supply knowledge necessary to the solution of this problem is the chief reason why the body is studied in our public schools.

*Divisions of the Subject.*--The body is studied from three standpoints: structure, use of parts, and care or management. This causes the main subject to be considered under three heads, known as anatomy, physiology, and hygiene.

Anatomy treats of the construction of the body--the parts which compose it, what they are like, and where located. Its main divisions are known as gross anatomy and histology. Gross anatomy treats of the larger structures of the body, while histology treats of the minute structures of which these are composed--parts too small to be seen with the naked eye and which have to be studied with the aid of the microscope.

Physiology treats of the function, or use, of the different parts of the body--the work which the parts do and how they do it--and of their relations to one another and to the body as a whole.

Hygiene treats of the proper care or management of the body. In a somewhat narrower sense it treats of the "laws of health." Hygiene is said to be personal, when applied by the individual to his own body; domestic, when applied to a small group of people, as the family; and public, or general, when applied to the community as a whole or to the race.

*The General Aim of Hygiene.*--There are many so-called laws of health, and for these laws it is essential in the management of the body to find a common basis. This basic law, suggested by the nature of the body and conditions that affect its well-being, may be termed the Law of Harmony: The mode of living must harmonize with the plan of the body. To live properly one must supply the conditions which his body, on account of its nature and plan, requires. On the other hand, he must avoid those things and conditions which are injurious, i.e., out of harmony with the body plan. To secure these results, it is necessary to determine what is and what is not in harmony with the plan of the body, and to find the means of applying this knowledge to the everyday problems of living. Such is the general aim of hygiene. Stated in other words: Hygiene has for its general aim the bringing about of an essential harmony between the body and the things and conditions that affect it.(1)

*Relation of Anatomy and Physiology to the Study of Hygiene.*--If the chief object in studying the body is that of learning how to manage or care for it, and hygiene supplies this information, why must we also study anatomy and physiology? The answer to this question has already been in part suggested. In order to determine what things and conditions are in harmony with the plan of the body, we must know what that plan is. This knowledge is obtained through a study of anatomy and physiology. The knowledge gained through these subjects also renders the study of hygiene more interesting and valuable. One is enabled to see why and how obedience to hygienic laws benefits, and disobedience to them injures, the body. This causes the teachings of hygiene to be taken more seriously and renders them more practical. In short, anatomy and physiology supply a necessary basis for the study of hygiene.

*Advantages of Properly Managing the Body.*--One result following the mismanagement of the body is loss of health. But attending the loss of health are other results which are equally serious and far-reaching. Without good health, people fail to accomplish their aims and ambitions in life; they miss the joy of living; they lose their ability to work and become burdens on their friends or society. The proper management of the body means health, and it also means the capacity for work and for enjoyment. Not only should one seek to preserve his health from day to day, but he should so manage his body as to use his powers to the best advantage and prolong as far as possible the period during which he may be a capable and useful citizen.

Chapter Ii - General View of the Body

*External Divisions.*--Examined from the outside, the body presents certain parts, or divisions, familiar to all. The main, or central, portion is known as the trunk, and to this are attached the head, the upper extremities, and the lower extremities. These in turn present smaller divisions which are also familiar. The upper part of the trunk is known as the thorax, or chest, and the lower part as the abdomen. The portions of the trunk to which the arms are attached are the shoulders, and those to which the legs are joined are the hips, while the central rear portion between the neck and the hips is the back. The fingers, the hand, the wrist, the forearm, the elbow, and the upper arm are the main divisions of each of the upper extremities. The toes, the foot, the ankle, the lower leg, the knee, and the thigh are the chief divisions of each of the lower extremities. The head, which is joined to the trunk by the neck, has such interesting parts as the eyes, the ears, the nose, the jaws, the cheeks, and the mouth. The entire body is inclosed in a double covering, called the skin, which protects it in various ways.

*The Tissues.*--After examining the external features of the body, we naturally inquire about its internal structures. These are not so easily investigated, and much which is of interest to advanced students must be omitted from an elementary course. We may, however, as a first step in this study, determine what kinds of materials enter into the construction of the body. For this purpose the body of some small animal should be dissected and studied. (See observation at close of chapter.) The different materials found by such a dissection correspond closely to the substances, called tissues, which make up the human body. The main tissues of the body, as ordinarily named, are the muscular tissue, the osseous tissue, the connective tissue, the nervous tissue, the adipose tissue, the cartilaginous tissue, and the epithelial and glandular tissue. Most of these present different varieties, making all together some fifteen different kinds of tissues that enter into the construction of the body.(2)

*General Purposes of the Tissues.*--The tissues, first of all, form the body. As a house is constructed of wood, stone, plaster, iron, and other building materials, so is the body made up of its various tissues. For this reason the tissues have been called the building materials of the body.

In addition to forming the body, the tissues supply the means through which its work is carried on. They are thus the working materials of the body. In serving this purpose the tissues play an active r˘le. All of them must perform the activities of growth and repair, and certain ones (the so-called active tissues) must do work which benefits the body as a whole.

*Purposes of the Different Tissues.*--In the construction of the body and also in the work which it carries on, the different tissues are made to serve different purposes. The osseous tissue is the chief substance in the bony framework, or skeleton, while the muscular tissue produces the different movements of the body. The connective tissue, which is everywhere abundant, serves the general purpose of connecting the different parts together. Cartilaginous tissue forms smooth coverings over the ends of the bones and, in addition to this, supplies the necessary stiffness in organs like the larynx and the ear. The nervous tissue controls the body and brings it into proper relations with its surroundings, while the epithelial tissue (found upon the body surfaces and in the glands) supplies it with protective coverings and secretes liquids. The adipose tissue (fat) prevents the too rapid escape of heat from the body, supplies it with nourishment in time of need, and forms soft pads for delicate organs like the eyeball.

*Properties of the Tissues.*--If we inquire how the tissues are able to serve such widely different purposes, we find this answer. The tissues differ from one another both in composition and in structure and, on this account, differ in their properties.(3) Their different properties enable them to serve different purposes in the body. Somewhat as glass is adapted by its transparency, hardness, and toughness to the use made of it in windows, the special properties of the tissues adapt them to the kinds of service which they perform. Properties that adapt tissues to their work in the body are called essential properties. The most important of these essential properties are as follows:

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