Excerpt from A Text-Book of Human Physiology. An animal organism in the living condition exhibits a series of phe homena which relate to growth, movement, mentality, and reproduction. During the period preceding birth, as well as during the period included between birth and adult life, the individual grows in Size and complexity from the introduction and assimilation of material from without. Through out its life the animal exhibits a series of movements, in virtue of which it not only changes the relation of one part of its body to another, but also Changes its position relatively to its environment. If, in the execution of these movements, the parts are directed to the overcoming of opposing forces, such as gravity, friction, cohesion, elasticity, etc., the'animal may be said to be doing work. The result of normal growth is the attainment of a physical development that will enable the animal, and, more especially, man, to perform the work necessitated by the nature of its environment and the character of its organization. In man, and probably in lower animals as well, mentality manifests itself as intellect, feeling, and volition. At a definite period in the life of the animal it reproduces itself, in consequence of which the species to which it belongs is perpetuated.. The study of the phenomena of growth, movement, mentality, and' reproduction constitutes the science of animal physiology. But as these general activities are the resultant of and dependent on the special activities of the individual structures of which an animal body is composed, physi ology in its more restricted and generally accepted sense is the science which investigates the actions or functions of the individual organs and tissues of the body and the physical and chemic conditions which underlie and deter mine them.. About the Publisher. Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com. This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.