86 CRITIQUES AND ADDRESSED [iv. 



to be that the parts exist for the sake of the whole and 

 the whole for the sake of the parts. But when Turpin 

 and Schwann resolved the living body into an aggrega- 

 tion of quasi-independent cells, each, like a Torula, 

 leading its own life and having its own laws of growth 

 and development, the aggregation being dominated and 

 kept working towards a definite end only by a certain 

 harmony among these units, or by the superaddition of 

 a controlling apparatus, such as a nervous system, this 

 conception ceased to be tenable. The cell lives for its 

 own sake, as well as for the sake of the whole organism ; 

 and the cells, which float in the blood, live at its 

 expense, and profoundly modify it, are almost as much 

 independent organisms as the Torulce which float in 

 beer-wort. 



Schwann burdened his enunciation of the " cell 

 theory " with two false suppositions ; the one, that the 

 structures he called " nucleus " and " cell-wall " are 

 essential to a cell ; the other, that cells are usually 

 formed independently of other cells; but, in 1839, it 

 was a vast and clear gain to arrive at the conception, 

 that the vital functions of all the higher animals and 

 plants are the resultant of the forces inherent in the 

 innumerable minute cells of which they are composed, 

 and that each of them is, itself, an equivalent of one of 

 the lowest and simplest of independent living beings 

 the Torula. 



From purely morphological investigations, Turpin and 

 Schwann, as we have seen, arrived at the notion of the 

 fundamental unity of structure of living beings. And, 

 before long, the researches of chemists gradually led up 

 to the conception of the fundamental unity of their 

 composition. 



So far back as 1803, Thenard pointed out, in most 

 distinct terms, the important fact that yeast contains a 



