The aim in the preparation of this treatise on the human body has been, first, to set forth in a teachable manner the actual science of physiology; and second, to present the facts of hygiene largely as applied physiology. The view is held that ''right living'' consists in the harmonious adjustment of one's habits to the nature and plan of the body, and that the best preparation for such living is a correct understanding of the physical self. It is further held that the emphasizing of physiology augments in no small degree the educative value of the subject, greater opportunity being thus afforded for exercise of the reasoning powers and for drill in the modus operandi of natural forces. In the study of physiology the facts of anatomy have a place, but in an elementary course these should be restricted to such as are necessary for revealing the general structure of the body.
e 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 rôle. 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