Book Description

Excerpt from Text-Book of Zoology: For Schools and Colleges On the other hand, the objects which belong to the animal and vegetable kingdoms differ from those which are comprised in the mineral kingdom in the following points: a. They are composed of few chemical elements, of which carbon, hydro gen, oxygen, and nitrogen, are the most important; and these elements are combined to form complex organic compounds, which always contain a large proportion of water, are very nu stable, and are prone to spontaneous decomposition. 6. They are composed of diverse or heterogeneous parts, which have usually more or less definite relations to one another. These heterogeneous but related parts are termed organs, and the objects possessing them are said to be organized. Some of the lowest forms of animals have bodies composed of so uni form a substance that they cannot be said to be organized, as they exhibit no definite organs. This exception, however, does not affect the general value of this distinction. 0. They are always more or less definite in shape, presenting concave and convex surfaces, and being bounded by curved lines. 07. When they increase in size, or grow, they do so, not by the addi tion of particles from the outside, but by the reception of foreign matter into their interior and its assimilation there (technically called intussusception e. They invariably pass through certain periodic changes in a definite and dis coverable order; these changes constituting life. They are subject to the same physical and chemical laws as those which govern dead matter, but the living body is the seat of some thing in virtue of which it can override the physical laws which enslave mere dead matter. The living body, so long as it is a living body, is the seat of energy, and can overcome the primary law of the inertia of matter. It has certain relations with the outer world other than the merely passive ones of dead matter. However humble it may be, and even if it be permanently rooted to one place, some part or other of every living body possesses the power of spontaneous and inde pendent motionma power possessed by nothing that is dead. In the higher animals the relations of the living body to dead nature become still further complicated, and their mastery over the physical forces becomes more and more pronounced. 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.