Natural History, strictly speaking, and as the term itself implies, should be employed to designate the study of all natural objects indiscriminately, whether these are endowed with life, or exhibit none of those incessant vicissitudes which collectively constitute vitality. So enormous, however, have been the conquests of science within the last century, that Natural History, using the term in its old sense, has of necessity been divided into several more or less nearly related branches.
In the first place, the study of natural objects admits of an obvious separation into two primary sections, of which the first deals with the phenomena presented by the inorganic world, whilst the second is occupied with the investigation of the nature and relations of all bodies which exhibit life. The former department concerns the geologist and mineralogist, and secondarily the naturalist proper as well; the latter department, treating as it does of living beings, is properly designated by the term Biology (from βios, life, and λoyos, a discourse). Biology, in turn,, may be split up into the sciences of Botany and Zoology, the former dealing with plants, the latter with animals; and it is really Zoology alone which is nowadays understood by the term Natural History. It should also be borne in mind that the science which deals with those forms of life which have existed during previous periods of the earth's history to the present, and which is usually designated by the separate title of Palaeontology, is, in all strictness, part and parcel of Biology proper, and has no relations but indirect ones with Geology. As living beings are divisible into animals and plants, so Palaeontology falls into the two branches of Palaeozoology and Palaeobotany, of which the former is inseparably united with Zoology or Natural History, while the latter is part of Botany as ordinarily understood. It is with animals and plants as organisms that Palaeontology has to deal, and the methods of palaeontological inquiry are those employed by the zoologist and the botanist. We must therefore assign to Biology a considerably wider domain than that which has been allowed to it by the earlier workers in the department of Natural History.
It will be obvious, then, that in the attempt to determine the limits and scope of Biology, we are brought at the very threshold of our inquiry to the question, What are the differences between dead and living bodies? Before considering this point, however, it will be advisable to discuss briefly the characters which in a general way distinguish what are known as "organic " from " inorganic" bodies.