Animal

(an'e-mal.) [L.] (Nat. Hist.) A living body endued with sensation and spontaneous motion. The difficulty of drawing the line of demarcation between the animal and vegetable kingdoms is acknowledged by all naturalists. The lowest forms of each are well nigh undistinguishable, and have been attributed by turns, first to one and then to the other domain of organized existence. It is, however, said that the best distinction hitherto ascertained is drawn from the fact that the food of plants consists of inorganic compounds, whilst animals require organized matter for their support, coupled with the facts that the alimentary matter of plants is absorbed through their external surface, no solid particles being taken in, while that of animals goes direct into their substance. A. Functions are those by which the materials that constitute and support the bodies of animals are prepared and supplied. The principal of these functions are the following: circulation, digestion, nutrition or a imilation, respiration, and secretion which are employed in producing animal matter from the substances that compose it, repairing waste, and getting rid of what is superfluous. But, besides these, there are others, which, though they do not act like the foregoing, are, in many animals, subservient to various important purposes.A. Heat is that property of all animals by which they preserve a certain temperature, quite independent of that of the medium by which they are surrounded, and is e entially nece ary to life. That of a man in health is from about 94° to 100° Fahr. Birds maintain a temperature of about 108° Fahr. This heat appears to depend upon the absorption of oxygen in the lungs, and throughout the body; carbonic acid being formed in the lungs by the union of oxygen with carbon, and water throughout the body by the union of oxygen with hydrogen-heat and vital energy being in both cases the result. Hence this general slow combustion, which is constantly going on in the body, is most intimately connected with the state of the nervous system. The heat of the human body remains nearly the same, when exposed to extreme degrees of temperature. Fishes, reptiles, and most invertebrate animals, are cold blooded. They have not the power of maintaining a uniform temperature, and their heat depends upon that of the surrounding medium.- The A. kingdom is generally divided by naturalists into 5 great branches or types, viz.: 1. Vertebrata (animals with a jointed back-bone); 2. Articulata (crabs, spiders, insects, worms); 3. Mollusca (shell-fish and their allies); 4. Radiata (sea-urchins and star-fishes); 5. Protozoa (sponges, foraminifera, .). [s. 32]