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Show 332 THE EG~. or shells, and both of these are found to contam lime, a substance of which most plants contain none., and some only a very little. But this lime, which, in itself, is not, strictly speaking, animal matter, is always in the living, or the 1·ecent state, cemented together by more or less of animal matter; and all animal matter contains nitrogen, which is usually 1·egarded as the inactive ingredient of atmospheric air. ·when the animal substance is burnt, a portion of the nitrogen combines with the hydrogen of watet", and forms ammonia; the peculiar pungent smell of which is well known in the solution usually called hartshorn, and which is always more or less perceptible when any animal matter is burnt. That smell is indeed the best test of the presence of animal matter in a state of decomposition. No inorganic substance is composed of the same ingredients as animal matter; and though some few vegetable products, such as Indian rubber, and the other juices alluded to, resemble animal matter, they are always accompanied in the same organization with other parts which are wholly and obviously vegetable. Thus, the "living principle," which is the name usually given to the fact of organization in a state of action, not only suspends those laws of mechanics and chymistry which inorganic matter always obeys, but has a chymistry and mechanics of its own, by means of which it can dissolve those substances which contain the materials necessary for the growth or the repair of its own structure, works these into the necessaty new compounds, and give~ them the proper form5 and consistencies. In any one instance, that, when we think of it, is truly wonderful, and should, one would suppose, make everybody take an interest in the thousands of living creatures with which all around us is peopled. Take, for example the egg of a bird. That may be found when not bigger than a grain of mus~ tard-seed: when the whole substance of it is yelk i THE EGG. 333 and the white which contains the embryo, or at least some portion of the embryo of the fut~re .bird, is a pellicle of so very pu!e. a texture that 1t Is. hardly discoverable. Well, It 1s brought to a certam stage of maturity by the action of the parent bird, just as a seed is ripened by the action of the parent plant. In that state it is an independent being, and is separated from its connexion with the parent. External causes to stimulate it into action are all that are now required for bringing it to the same state as the parent, but it must hav~ the. sti~ulus of these, otherwise it not only remams mactlvc, but becomes putrid-yields to the laws of matter, and passes into the mass of materials. It may be kept perfect for a considerable time, if the air is completely excluded, but there is. reason to suppose _t~at it would in time undergo mternal decomposition even then, in much less time than the seed of a plant, if so protected, would take before it lost the power of germination. . But still the egg is a very wonderful thmg; and were it not that we are so familiar with it, we would 0'0 farther to see it than to see most of the subjects ~hich engage our attention. It is handsome in its form, and every way beautiful to look at; ~o that a collection of eggs forms by no means an umnteresting cabinet-if the possessor can tell the tales ?f the birds. But the wonderful part of the matter Is, that a body of the form of a pebble, and consisting of a thin shell of lime, lined with a soft membrane, and having within it first a transparent and theJ?- a yellow jelly, should have the power, by the actiOn of heat and air alone, of evolving a vast number of animal organs and substances, all differing from each other in different kinds of eggs ; but never deviating so far from the characters of the parent birds as that they cannot be instantly discerned to belong to the same species, and display to a very great extent the same phenomena, and the same |