156 The Unity of the Organism 



Schwann, he "defines it," Hertwig says, "as a bit of proto- 

 plasm endowed with life, in which lies a nucleus." ! 



Almost simultaneously with this insight by Schultze, Carl 

 Briicke, contemplating cells from the standpoint of their 

 complex structure as well as from that of their ensemble of 

 life activities, advanced to the conception of the cell as an 

 organism. 



The language in which Briicke expresses himself on this 

 point is of sufficient interest to warrant quoting: "We 

 must ascribe to the living cell, in addition to the molecular 

 structure of the organic compounds which it contains, still 

 another and a differently constituted structure, and it is 

 this which we designate as organization " IQ And in another 

 connection he introduces the phrase, now firmly established 

 in biology, elementary organism, as a designation for the 

 cell. 



One of the securest aspects of the cell-theory was reached 

 only when the conception organism was applied to the cell. 

 Both historically and logically, the organism is made to do 

 duty in interpreting the cell. Whatever validity the con- 

 ception cell has in the modern cell-theory, is due in large 

 measure to whatever validity the conception organism has. 

 But the conception organism was well established in biology 

 long before the conception cell was; hence the justification 

 of the statement that historically the organism interprets 

 the cell. Organism as an idea is prior and contributory to 

 cell as an idea. That logically also the cell is partly in- 

 terpreted by the organism is seen in the fact that observers 

 agree in ascribing to the cell the most distinctive attributes 

 of the organism : namely those of metabolism, reproduction, 

 response to stimuli, etc. 



Our birds-eye view of the cell-theory enabled us to see 

 that if it be held in the broad sense in which it is con- 

 ceived by many but not by all biologists, it consists of two 

 parts : one a firmly established generalization of observed 



