This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
Human Physiology is that department of science which has for its object the discovery and accurate description of the properties and actions of the living healthy human body, and the finding of the uses or (as physiologists call them) the functions, of its various parts. Physiologists endeavor to discover what the body, as a whole, does while alive, and what each part of it does, and how it does it; also under what conditions the work of the body is best performed; and, in connection with this last aim, to furnish the basis of Hygiene, the science which is concerned with the laws and conditions of health.
What is human physiology? What is a function? What do physiologists endeavor to discover? What is meant by Hygiene?
Clearly, the first step to be taken towards finding out the use and mode of working of each part of the body is to find out what the parts are ; this study is known as Human Anatomy. Examined merely from the exterior, the body is quite a complicated structure: we can all see for ourselves, head and neck, trunk and limbs, and even many smaller but quite distinct parts entering into the formation of these larger ones, as eyes, nose, ears, and mouth; arm, forearm, and hand ; thigh, leg, and foot. This knowledge of its complexity, which we may all arrive at by looking on the outside of the body, is vastly extended when it is dissected and its interior examined ; we then learn that it is made up of many hundreds of diverse parts, each having its own structure, and form, and purpose, but all harmoniously working together in health.
Anatomy is concerned with the form and structure and connections of the parts of the body. Physiology with the uses of the parts, and the ways in which they work. Hygiene with the conditions of life which promote the health of the body.