This section is from the book "Human Physiology For The Use Of Elementary Schools", by Charles Alfred Lee. Also available from Amazon: Human Physiology, for the Use of Elementary Schools.
14. This power of resisting the mechanical and chemical laws of matter, is shown by the faculty which animal bodies possess of maintaining the same degree of temperature, amid the great changes from heat to cold to which they are exposed; in the power of changing to chyle and blood, the various forms of food on which they subsist; and also in their power of forming from these the various tissues and organs of which they are composed, and all in opposition to the general laws of matter.
15. The growth of organized bodies proceeds from within, that of inorganic matter from without. If minerals increase in size, it is by attracting matter to their external surface, while animals and vegetables grow by a process, called nutrition ; that is, laying hold of nutritious substances and converting them to their own nature, by means of internal organs.
16. Organized bodies possess the power of being affected with disease and recovering from it. They also have a determinate duration, beyond which they do not often live. This period varies for each species of animal and vegetable. Some insects live but a single day ; most plants live but a single year; but some trees, such as the oak and cedar, are supposed to live more than two thousand years. The average duration of human life in this country is not over thirty years.
17. But the great distinction between a living being and an inorganic body is, that the former carries on a number of processes, not performed by the latter. A plant, for example, absorbs food, converts it into its own proper substance, arranges it into bark, wood, leaves, and other organized structures, grows, arrives at maturity, generates and maintains a certain degree of heat, decays, and finally perishes. No such phenomena are exhibited by a stone, or other inorganic bodies. These processes, therefore, are called vital, because they are peculiar to a state of life and afford characters by which a living being is distinguished from all others.
18. Organized beings are divided into two classes, animals and vegetables, differing from each other in several well known features.
19. Sensation and voluntary motion are possessed by animals, but not by vegetables. Had animals no sensibility or feeling, they could not know their wants ; and if they knew them but had not the power of motion, they would perish for want of food ; hence the necessity of these two faculties being joined together.
20. An animal, like a plant, receives food, transforms it into its own proper substance, and builds it up into certain structures ; it also generates and maintains a certain degree of temperature, and after having arrived at maturity decays and dies; but in addition to these vital processes which are similar in both, the animal possesses the faculty of feeling and moving spontaneously, or according to the dictates of its will, a property peculiar to itself.
21. Vegetables are nourished by the substances immediately around them, such as air, water, and the saline properties of the soil. They draw their support from without, by absorption at their surface, or by means of roots. But animals draw their nutriment from a great variety of sources, and they are furnished with an internal cavity to receive and prepare it for the purposes of nourishment.
22. Vegetable matter is composed chiefly of three elements, viz. carbon, hydrogen, and oxygen; besides these, animal matter contains azote, which gives the peculiar smell that we perceive on burning flesh, hair, bones, or feathers. Eighteen simple substances, however, have been found in vegetables, in very small quantities;, such as lime, sulphur, iodine, silex, potash, soda, etc.
23. Animals and vegetables both eonsist of solid and fluid parts; the fluids, however, in animals, exist in much the largest proportion. This is the reason why decomposition occurs more rapidly in animals than in vegetables. Vegetables, abounding in fluids, decay sooner than those of a more solid or fibrous texture.
24. Though the differences between animals and vegetables, are in general sufficiently obvious and striking, yet in some few instances, their distinguishing characteristics are not so evident. This is apparent from the fact, that some animals have been mistaken for vegetables, and some vegetables for animals. Some animals we find to be as firmly attached to the soil, as most vegetables are, as is the case in many of the zoophytes, or lowest order of animals, as the sponge, coral, etc. ; while on the other hand, some vegetables float in the water, as many kinds of sea weed, and are never attached to the soil.
What is physiology ? What does vegetable physiology treat of ? What human ? What classes does the kingdom of nature embrace ? What other division ? What is meant by organic bodies ? What by inorganic ? How are organic bodies divided ? How do organic and inorganic bodies differ from each other ? How do they differ as to form ?-as to size ?-as to their number of elements ?-as to their mode of combination ?-as to the shape of their particles ?-as to the changes they undergo ?-as to the mutual dependence of parts ?-as to the kinds of elements ?-as to their general properties ? How as to their mode of growth ? of disease ? What is the grand distinction between the two classes of bodies ? How are organized beings divided ? How do animals and vegetables differ ? How are vegetables nourished ? What is vegetable matter composed of? Do animals or vegetables possess the greatest amount of fluids ? What animals have been mistaken for vegetables ?