CHAPTER I 



THE HISTORY OF THE SUBJECT 



Contents: Introductory. Earliest period. Francis Glisson as founder of 

 the doctrine of irritability. Albrecht von Haller. The vitalists. Bor- 

 den and Barthez. John Brown's system. Johannes Muller and the 

 specific energy of living substance. Rudolf Virchow's doctrine of the 

 irritability of the cell. Discovery of the inhibitory effects of stimu- 

 lation. Weber, Schiff, Golts, Setschenow, Sherrington. Claude Ber- 

 nard studies on narcosis. Tropisms. Ehrenberg, Engelmann, Pfeffer, 

 Strassburgcr, Stahl. Semon's speculations on mneme. 



Irritability is a general property of living substance but not 

 exclusively so. Irritable systems also exist in inanimate nature. 

 What characterizes living substances is not irritability as such, 

 but an irritability of a specific type. The irritability of the living 

 system can, therefore, not be studied alone, but as the properties 

 of a living system are dependent upon each other, so this property 

 must be considered with the others possessed by a living sub- 

 stance. In this sense irritability presents a problem of funda- 

 mental physiological importance. For if we could analyze the 

 irritability of living substance to its essence, then the nature of 

 life itself would be fathomed. The analysis of irritability of 

 living substance oflfers us, therefore, a path to the investigation 

 of life and herein lies the importance of the study of irritability. 



I wish to follow this path toward the knowledge of the vital 

 processes and to endeavor to show in these lectures what informa- 

 tion the analysis of irritability and that of the effect of stimuli 

 can give us of the mechanism of the processes in living substance. 

 Before doing so, however, I wish to consider somewhat more in 

 detail the question as to how we have arrived at the conception 

 of the nature of irritability. 



