88 THE STORY OF LIFE'S MECHANISM. 



of the fully formed animal or plant, however 

 complex, are simply the application of mechani- 

 cal and chemical principles among the groups ol 

 such cells. But wherein does this knowledge of 

 cells help us 1 Are we any nearer to understand- 

 ing how these vital processes arise ? In answer 

 to this question we may first ask whether it is 

 possible to determine whether any one part of 

 the cell is the seat of its activities. 



THE CELL WALL. 



The first suggestion which arose was that the 

 cell wall was the important part of the cell, the 

 others being secondary. This was not an un- 

 natural conclusion. The cell wall is the most 

 persistent part of the cell. It was the part first 

 discovered by the microscope and is the part 

 which remains after the other parts are gone. 

 Indeed, in many of the so-called cells the cell 

 wall is all that is seen, the cell contents having 

 disappeared (Fig. 14). It was not strange, then, 

 that this should at first have been looked upon 

 as the primary part. The idea was that the cell 

 wall in some way changed the chemical character 

 of the substances in contact with its two sides, 

 and thus gave rise to vital activities which, as 

 we have seen, are fundamentally chemical. Thus 

 the cell wall was regarded as the most essential 

 part of the cell, since it controlled its activities. 

 This was the belief of Schwann, although he also re- 

 garded the other parts of the cell as of importance. 



This conception, however, was quite temporary. 

 It was much as if our hypothetical supramundane 

 observer looked upon the clothes of his newly 



