THE CELL AND PROTOPLASM. 137 



build machines by the adjustment of parts to each 

 other. But this topic belongs to the second part 

 of our subject, and must be for the present post- 

 poned. 



REACTION AGAINST THE CELL DOCTRINE. 



As the knowledge of cells which we have out- 

 lined was slowly acquired, the conception of the 

 cell passed through various modifications. At 

 first the cell wall was looked upon as the funda- 

 mental part, but this idea soon gave place to the 

 belief that it was the protoplasm that was alive. 

 Under the influence of this thought, the cell 

 doctrine developed into something like the fol- 

 lowing : The cell is simply a bit of protoplasm 

 and is the unit of living matter. The bodies of 

 all larger animals and plants are made up of 

 great numbers of these units acting together, 

 and the activities of the entire organism are 

 simply the sum of the activities of its cells. 

 The organism is thus simply the sum of the 

 cells which compose it, and its activities the 

 sum of the activities of the individual cells. 

 As more facts were disclosed the idea changed 

 slightly. The importance of the nucleus became 

 more and more forcibly impressed upon micro- 

 scopists, and this body came after a little into 

 such prominence as to hide from view the more 

 familiar protoplasm. The marvellous activities 

 of the nucleus soon caused it to be regarded as 

 the important part of the cell, while all the rest 

 was secondary. The cell was now thought of as 

 a bit of nuclear matter surrounded by secondary 

 parts. The marvellous activities of the nucleus, 



