The philosophy of natural history / by William Smellie ; with an introduction and various additions and alterations intended to adapt it to the present state of knowledge by John Ware.

  • Smellie, William, 1740-1795.
Date:
1827
Catalogue details

Licence: Public Domain Mark

Credit: The philosophy of natural history / by William Smellie ; with an introduction and various additions and alterations intended to adapt it to the present state of knowledge by John Ware. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

    15/338
    In the second place, living bodies differ as to the mode of their existence, in so much as they are dependant upon other things beside themselves for the continuance of that existence. The matter of which they are composed, is constantly changing. This matter is, in fact, only common matter endowed for a certain period with the powers of life, in consequence of being united to living systems. By the various internal operations constantly going on, part of this matter is expended, is sent out of the system ; this loss must be repaired by the addition of new mat- ter. Hence the necessity of nourishment to the support of life; hence the necessity of a regular supply, to every thing living, of a certain quantity of food adapted in kind to the nature of the individual. This food is operated upon by the organs of the animal or vegetable, is assimilated to it, and its properties are modified until it becomes fit to make a component part of it. This is nutrition, an essential process of living bodies, by which they are enabled to increase in size and strength, to modify the structure of their different parts, and to maintain them in a fit state for performing the offices for which they are designed. Minerals, on the contrary, have no such dependance; the matter of which they consist is always the same; they con- tain within themselves every thing which is essential to their existence, and have, of course, no necessity for nutrition or growth. It is true that these substances sometimes increase in size, as happens with regard to stalactites, the deposition of crystals, and the formation of alluvia. But there is this marked difference between all such instances of growth, and that of animals or vegetables; that, in the former case, it amounts to the mere juxtaposition of similar particles, unchanged in their nature ; whilst in the latter the particles are changed in their nature, and subjected to the operation of entirely new laws. In the former case, the growth depends upon a principle operating from without; in the latter, upon a principle operating from within. But, in the third place, though dependant upon other sub- stances in this way for the means of continuing their existence, living bodies possess in another point of view a kind of independ- ence upon all other matter. They are removed, by the possession of the powers of life, in a certain degree out of the influence of physical and chemical laws ; they contain within themselves a principle by which they are enabled directly to resist the opera- tion of those laws, which would otherwise ensure their speedy destruction. They depend upon the things around them for the