THE CELL AND PROTOPLASM. 75 



plasm, and nothing more. But the more impor- 

 tant feature of this doctrine was not the simple 

 conclusion that the cell substance constitutes the 

 cell, but the more sweeping conclusion that this 

 cell substance is in all cells essentially identical. 

 The study of all animals, high and low, showed 

 all active cells filled with a similar material, and 

 more important still, the study of plant cells dis- 

 closed a material strikingly similar. Schultze ex- 

 perimented with this material by all means at his 

 command, and finding that the cell substance in 

 all animals and plants obeys the same tests, 

 reached the conclusion that the cell substance in 

 animals and plants is always identical. To this 

 material he now gave the name protoplasm, choos- 

 ing a name hitherto given to the cell contents of 

 plant cells. From this time forth this term proto- 

 plasm was applied to the living material found in 

 all cells, and became at once the most important 

 factor in the discussion of biological problems. 



The importance of this newly formulated doc- 

 trine it is difficult to appreciate. Here, in proto- 

 plasm had been apparently found the foundation 

 of living phenomena. Here was a substance uni- 

 versally present in animals and plants, simple and 

 uniform a substance always present in living 

 parts and disappearing with death. It was the 

 simplest thing that had life, and indeed the only 

 thing that had life, for there is no life outside of 

 cells and protoplasm. But simple as it was it had 

 all the fundamental properties of living things 

 irritability, contractibility, assimilation, and repro- 

 duction. It was a compound which seemingly 

 deserved the name of " physical basis of life" which 

 was soon given to it by Huxley. With this con- 

 ception of protoplasm as the physical basis of life 



