THE CELL A UNIT OF LIFE. 1 23 j 



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has been regarded during the last thirty-five years as the 



true basis of all morphological and physiological know- \ 



ledge in Zoology and Botany, it is especially necessary to 



conceive the cell as an integral organism, or, in other words, 



an independent living being. When by dissection we have ' 



separated the developed body of a Man, or of any other | 



animal or plant, into its organs, and when we then proceed | 



further to examine by means of the microscope the more | 



minute constituents of these larger organs, which give the 



form to the whole organism, we are surprised to find that all ' 



these various parts are made up of the same fundamental I 



constituents or structural elements ; and these are cells. ' 



Whether we examine anatomically and by means of the ! 



microscope, a leaf, a flower, or a fruit ; or again, a bone, a 



muscle, a gland, or a piece of skin, etc., we everywhere find 1 



one and the same form-element, which has been called the i 



Cell, since Schleiden gave it that name. Very different , 



views are held as to the real nature of this cell ; but what- ! 



ever we think of it, it must be regarded as an independent 



life-unit. The tiny cell is, as Briicke says, " an elementary 



organism," or, as Yirchow expresses it, a " seat of life " 



{Lebensheerd). It is, perhaps, most accurately described as ! 



the organic unit of form of the lowest grade, as an indi- : 



vidual of the first order (Generelle MoyyJiologie, vol. i. i 



p. 269). This unit is such both in anatomical form, and in 



physiological function. In the Protista, in the one-celled i 



plants and primitive animals, the whole organism per- [ 



manently consists only of a single cell. On the contrary, in 



most animals and plants, it is only in the earliest period 



of individual existence that the organism is a simple cell ; 



it afterwards forms a cell-society, or, more correctly, an ' 



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