THE CELL-THEORY 253 



Examining his statements closely, we notice, indeed, that his 

 imperfect means of investigation led Wolff into two important errors 

 — that of supposing the cells of plants to communicate in their 

 youngest state, and thence deducing a false analogy with the areolar 

 tissue of animals ; and that of supposing that animal and vegetable 

 tissues are always, in their very youngest state, absolutely structureless. 

 However, as we shall see subsequently, Wolff is by no means singular 

 in having started with grave anatomical mistakes, and we cannot 

 perceive that in his case these errors, one of which, at any rate,, 

 Schleiden shares with him, vitiate those other and more important 

 parts of his views, to which we are about to refer. 



We have said, in fact, that not merely speculatively, but by 

 observation, Wolff established a theory of the development of the 

 vegetable tissues very similar to that of Schleiden, and that " identity 

 of structure as shown by their development," between plants and 

 animals, to prove which, was the purpose of the microscopical investi- 

 gations of Schwann. But he did much more than this. In the ' Theoria, 

 Generationis,' and in the essay on the vital forces published thirty 

 years afterwards, Wolff developed some very remarkable views on the 

 relation of life to organization — of the vital processes to the organic 

 elements — in which he diverges very widely from all who preceded,, 

 and from most who have followed him, most of all from Schleiden and 

 Schwann. We may best exhibit the bearing of these views by 

 contrasting them with those of the latter writers. 



Schleiden and Schwann teach implicitly that the primary histological 

 elements (cells) are independent, anatomically and physiologically ; 

 that they stand in the relation of causes or centres, to organization and 

 the " organizing force ; " and that the whole organism is the result of 



p. 63; ". . . .so, from the case of many other attractions, especially of crystallization, 

 which, among all known phenomena, comes nearest to vegetation, that without the second 

 property — viz., that by means of which the mutually attractive substances interpenetrate and 

 mingle with one another — the attractive force, although it should possess the first property, 

 yet could as little effect nutrition. The particles of a salt dissolved in water attract only 

 particles of salt — i.e., homogeneous substances, and repel all heterogeneous matters; for 

 we get pure (crystals of the) salts. But out of this attraction comes nothing that can be 

 compared with nutrition ; for although the whole mass of substance is increased by degrees, 

 yet crystals once formed remain as they are, and are not increased in their substance, and 

 nothing less than the formation of new organization and continual change of figure accom- 

 panies this increase Crystals once formed attract the saline particles only to their 



outer surface, upon which the attracted parts are deposited. They do not attract these 

 particles into their substance. . . .If the saline particles, on the other hand, penetrated 

 the crystals and increased their substance homogeneously in all parts, this process would be 

 indistinguishable from nutrition, and would consequently be a true nutrition." Compare 

 Schwann, pp. 239-.-257. 



