THEODOR SCHWANN 251 



organism. It may, indeed, be said of the ova of higher animals, that 

 after impregnation the ovum is essentially different from the other 

 cells of the organism; that by impregnation there is a something 

 conveyed to the ovum, which is more to it than an external condition 

 for vitality, more than nutrient matter ; and that it might thereby have 

 first received its peculiar vitality, and therefore that nothing can be 

 inferred from it with respect to the other cells. But this fails in 

 application to those classes which consist only of female individuals, 

 as well as with the spores of the lower plants ; and, besides, in the in- 

 ferior plants any given cell may be separated from the plant, and then 

 grow alone. So that here are whole plants consisting of cells, which 

 can be positively proved to have independent vitality. Now, as all 

 cells grow according to the same laws, and consequently the cause of 

 growth cannot in one case lie in the cell, and in another in the whole 

 organism ; and since it may be further proved that some cells, which 

 do not differ from the rest in their mode of growth, are developed 

 independently, we must ascribe to all cells an independent vitality, that 

 is, such combinations of molecules as occur in any single cell, are 

 capable of setting free the power by which it is enabled to take up 

 fresh molecules. The cause of nutrition and growth resides not in 

 the organism as a whole, but in the separate elementary parts — the 

 cells. The failure of growth in the case of any particular cell, when 

 separated from an organized body, is as slight an objection to this 

 theory as it is an objection against the independent vitality of a bee, 

 that it cannot continue long in existence after being separated from 

 its swarm. The manifestation of the power which resides in the cell 

 depends upon conditions to which it is subject only when in connexion 

 with the whole (organism). 



The question, then, as to the fundamental power of organized bodies 

 resolves itself into that of the fundamental powers of the individual 

 cells. We must now consider the general phenomena attending the 

 formation of cells, in order to discover what powers may be presumed 

 to exist in the cells to explain them. These phenomena may be ar- 

 ranged in two natural groups : first, those which relate to the combina- 

 tion of the molecules to form a cell, and which may be denominated 

 the plastic phenomena of the cells ; secondly, those which result from 

 chemical changes either in the component particles of the cell itself, 

 or in the surrounding cytoblastema, and which may be called meta- 



