152 CELLS OF THE VERTEBRATE BODY 



mals are to be explained in terms of simple cell and tissue reac- 

 tions, built up into complex activities as a result of the coordina- 

 tions that produce the phenomena of individuation. 



The emphasis placed upon the activities of individual cells as the 

 basis for the interpretation of bodily processes as a whole, and the 

 analysis of all structures in terms of cells and cell products should 

 make clear how fundamental is the generalization embodied in the 

 Cell Doctrine. As animals other than the vertebrates are studied, 

 it will be seen that cells, and their requirements and responses, are 

 essentially the same throughout the realm of living organisms. 

 The Doctrine of Organic Evolution alone takes rank with the Cell 

 Doctrine as a unifying conception in biological science. 



