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Show 10 INTRODUCTION • this primitive adhesion to a similar bei~g, is a rule wit~out exception. The separation of the germ 1s called gencr~tz~n. Every organized being re-produces others that are s1m1lar to itself, otherwise, death being a necessary consequence of life, the species would become extinct. . . Organized beings have even the faculty of reproducmg,. m degrees varying with the species, particular parts of which they may have been deprived-this is called the power of re-production. . The development of organized beings is more or less rapid, and more or less extended, as circumstances are more or less favourable. Heat the abundance and species of nutriment, with other causes ' 'exercise great influence, and this .in fluence may extend to the whole body in general, or to eerta1n organs · in particular: thence arises the impossibility of a perfect similitude between the offspring and parent. Differences of this kind, between organized beings, form what are termed varieties. There is no proof, that all the differences which now dis· tinguish organized beings, are such as may have been produced by circumstances. All that has been advanced upon this subject is hypothetical. Experience, on the contrary, ap· pears to prove, that, in the actual state of the globe, varieties are confined within rather narrow limits, and go back as far as we may, we still find those limits the same. We are thus compelled to admit of certain forms, which, from the origin of 'things, have perpetuated themselves with· out exceeding these limits, and every being appertaining to one or other of these forms, constitutes what is termed a spe· cies. Varieties are accidental subdivisions of species. Generation being the only means of ascertaining the limits to which varieties may extend, species should be defined, the 1·e-union of individuals descended one from the other, or from common parents, or from such as resemble them, as strongly as they 1·esemble each other. But although this definition is strict, it will be seen that its application to particular indivi· duals may be very difficult, where the necessary experiments have not been made. INTRODUCTION. 11 Thus then it stands-absorption, assimilation, exhalation, development and generation are functions common to all living bodies; birth and death the universal limits of their existence; an areolar, contractile tissue, containing within its laminre fluids or gases in motion, the general essence of its structure ; substances almost all susceptible of conversion into fluids or gases, and combinations capable of an easy and mutual transformation, the basis of their chemical composition. Fixed forms that are perpetuated by generation distinguish their species, determine the complication of the secondary functions proper to each of them, and assign to them the parts they are to play on the great stage of the universe. These forms are neither produced nor changed by their own agency-life supposes their existence, its flame can only be kindled in an organization already prepared, and the most profound meditation and lynx-eyed and delicate observation can penetrate no farther than the mystery of the pre-existence of germs. IJivision of Organized Beings into .JJ.nimals and Vegetables. Living or organized beings have always been subdivided into animate beings, that is, such as are possessed of sense and motion, and into inanimate beings, which arc deprived of both these faculties, and are reduced to the simple faculty of vegetating. Although the leaves of several plants shrink from the touch, and the roots are steadily directed towards moisture, the leaves to light and air, and though parts of vegetables appear to oscillate without any apparent external cause, still these various motions have too little similarity to those of animals, to enable us to find in them any proofs of perception or will. The spontaneity in the motions of animals required essential modifications even in their purely vegetative organs. Their roots not penetrating the earth, it was necessary they should be able to place within themselves a supply of aliment, and to carry its reservoir along with them. Hence is derived the first character of animals, or their alimentary caua1, from I |