96 Trams. Acad. Set. of St. Louis. 



resorption in the epithelium- cell and the white blood-cell; 

 that of the regulation of all bodily activities in the ganglion- 

 cell. ♦ **!£, then, physiology considers its task to 

 be the investigation of vital phenomena, it must investigate 

 them in the place where they have their seat, that is, in the 

 cell.'' * 



Ever since the formulation of the cell-theory the fact has 

 become more and more generally recognized that the solution 

 of all ultimate problems of biology is to be found in cell-in- 

 vestigation. Already the doctrine has contributed to the 

 science many of its most important generalizations. **It 

 was the cell-theory that first brought the structure of plants 

 and animals under one point of view by revealing their com- 

 mon plan of organization. It was through the cell-theory 

 that Kolliker and Kemak opened the way to an understanding 

 of the nature of embryological development, and the law of 

 genetic continuity lying at the basis of inheritance. It was 

 the cell-theory again which, in the hands of Virchow and 

 Max Schultze, inaugurated a new era in the history of physi- 

 ology and pathology, by showing that all the various func- 

 tions of the body, in health and in disease, are but the out- 

 ward expression of cell-activities. And at a still later day it 

 was through the cell-theory that Hertwig, Fol, Van Beneden 

 and Stragburger solved the long-standing riddle of the fertil- 

 ization of the eggy and the mechanism of hereditary trans- 

 mission. No other biological generalization, save only the 

 theory of organic evolution, has brought so many apparently 

 diverse phenomena under a common point of view or has ac- 

 complished more for the unification of knowledge. The cell- 

 theory must, therefore, be placed beside the evolution-theory 

 as one of the foundation stones of modern biology." t 



As early as the seventeenth century Hooke, Malpighi and 

 Grew had discovered in plant bodies, by the aid of low mag- 

 nifying glasses, small spaces, surrounded by firm walls and 

 filled with fluid, to which Hooke first applied the word cell. 

 The discovery attracted little or no attention and it was not 

 until nearly two centuries later that the cell was re-discovered. 



♦ Verworn, General Physiology, p. 48. 1899. 



t Wilson, The Cell in Development and Inheritance, p. 1. 1898. 



