OF CELLS AND CELL-LIFE. 129 



108. We have now to inquire into the nature of those peculiar phenomena, 

 of which Cells are the instruments, and to which the designation of Vital is given, 

 on account of their restriction to the living organism, and their distinctness from 

 those of a physical or chemical nature. The series of actions constituting Cell- 

 Development, under whichever of the foregoing modes it may take place, is, of 

 all these phenomena, that which stands in most complete opposition to anything 

 displayed by the Inorganic world ; and we see in it the type of the development 

 of the entire fabric, which essentially consists in the continual multiplication of 

 its component cells by one or other of the processes just described, and in the 

 subsequent changes which they undergo. Thus we observe the appropriation of 

 certain nutrient materials, derived from external sources, in the first extension 

 of the cell-wall, the enlargement of the nucleus, and the collection and increase 

 of the cell-contents ; and upon these materials a certain degree of transformation 

 is commonly exerted. As already pointed out ( 17), there is but little if any 

 chemical change needed for the incorporation of the nutrient materials with which 

 the Animal cell is supplied, into its own substance ; the cell-walls and nuclei 

 being apparently of the same chemical nature with the constituents of the blood, 

 at the expense of which they are developed : but we must here recognize a vital 

 change, in virtue of which they are rendered henceforth capable of exhibiting 

 actions, which, so long as they remain mere chemical compounds, they are utterly 

 unable to perform. The cell-contents, on the other hand, for the most part 

 remain as mere chemical compounds; and though they are in many instances 

 directly furnished by the nutrient fluid, there are other cases in which their com- 

 position is so different from that of anything it can be shown to include, that we 

 must reckon, as one manifestation of the peculiar attributes of the cell, the power 

 of Chemical Transformation. But its power may be also exerted in vitalizing 

 its contents or a certain portion of them ; this power of Vital Transformation 

 being probably possessed in a low degree by many cells which prepare the nu- 

 trient material for its appropriation by the living tissues, but being pre-eminently 

 the endowment of those which are concerned in the generative operations. 

 Thus, then, in the simple act of Cytogenesis, we recognize a force in operation 

 which converts certain chemical compounds into a living organized structure, not 

 only moulding them into a peculiar and characteristic form, but endowing them 

 with new attributes. And not the least remarkable of these attributes is that 

 power of increase and multiplication, whereby the same alterations may be effected 

 in an almost unlimited amount of raw material; so that an aggregation of organ- 

 ized tissue, sufficient to produce a fabric of considerable dimensions, may be 

 thereby generated from a single primordial cell. 



109. The history of the life of a Cell is by no means completed, however, by 

 the fullest enumeration of the successional phenomena exhibited in its develop- 

 ment and multiplication ; for, after it has attained its full growth, it may itself 

 undergo alterations of various kinds, or may become the instrument of effecting 

 changes in others, such as can scarcely be regarded in any other light than as 

 manifestations of a force identical with that which was operative in its original 

 production. Among the changes occurring in the cell itself, that which may 

 be first noticed is the permanent alteration mform which certain cells undergo, 

 not from forces external to them, but from agencies at work in their interior. 

 Thus, although spheroidal cells may be converted into polygonal by mutual 

 pressure on all sides, or may be lengthened towards the fusiform shape when 

 that pressure is less in one direction than in another, or may be flattened down 

 into a scale by the loss of its fluid, yet it is impossible to account in any such 

 mode for the extraordinary elongation of certain cells, or for the flattening of 

 others, when no pressure is being exerted upon them; or for the extension of 

 offsets from others into caudate or stellate prolongations ( 146). Some of these 

 cases are not improbably to be accounted for by the extension of the cell, whilst 



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