20 THE CELL DOCTRINE. 



the living mass, or what Wolft' calls the vis essentialis. 

 For him, however, this vis essentialis is no Archceus, 

 hut simply a convenient name for two facts which 

 he takes a great deal of trouble to demonstrate ; the 

 first, the existence in living tissues (before any pas- 

 sages are developed in them), of currents of the nu- 

 tritious fluid determined to particular parts by some 

 power which is independent of all external influence ; 

 and the second, the peculiar changes of form and 

 composition, which take place in the same manner."* 

 'Two points are here particularly to be observed as 

 cardinal, — first, the non-independence of cells, either 

 anatomically or physiologically ; that they are effects, 

 passive 'results, and not muses of a vitalizing or or- 

 ganizing force ; second, that organization takes place 

 from the " differentiation " of the homogeneous 

 living mass in these parts, through the agency of the 

 vis .essentialis or inherent vital force. The radical 

 difterence between these principles of development 

 and those generally held at the present day, will be 

 better appreciated when these latter have been 

 worked out. An acknowledged error may, however, 

 be pointed out, — the probable result of the inferiority 

 of the instruments of that day — that of supposing 

 the cells of plants and animals in all instances to 

 communicate when in their youngest state, and in 

 the latter to continue thus in communication through- 

 ,out life. It will be observed, also, that this theory 

 involved the spontaneous origin of the cell, that is, 

 independent of any previously existing cell. 



* Huxley, loo. citat., p. 293-4. Wolff, 0. P., Theoria Genera- 

 tionis, 1769. Ed. Nova, Halae, 1774. 



