THE HISTORY OF THE SUBJECT 5 



more so, because Glisson from the very first connected the irri- 

 tabiHty of the Hving substance through its possessing universal 

 energy with the phenomena in nature generally, just as we do 

 today two hundred years after, on the basis of the modern teach- 

 ings of energy. 



It might appear strange that a teaching of such fundamental 

 importance as that of Glisson's theory of irritability was not at 

 once accepted on all sides and further developed. There were 

 two reasons, however, which prevented this. Firstly, Glisson did 

 not devote himself to his post of teacher at the University of 

 Cambridge with any particular zeal and so consequently did not 

 establish a school of his own, to further work out and develop 

 his ideas. Secondly, his doctrines were so speculative and diffi- 

 cult to understand, his differentiations and definitions so artificial 

 and labored, that it required the greatest effort to penetrate to 

 his fundamental conceptions and so it happened that Glisson's 

 theory of irritability received attention only at a comparatively 

 late date. Even then, of his speculative theories hardly more than 

 the name "doctrine of irritability" was adopted. Since the middle 

 of the eighteenth century this name, however, was destined to lead 

 to excited controversies. 



The first attempt to give Glisson's expression "irritability" a 

 more concrete meaning was made by Haller ( 1708-1777) \ 

 Unfortunately, though, he confined this conception solely to 

 muscles, in that he understood by the term irritability "the capa- 

 bility of the muscles to contract, when stimulated, as the result 

 of vital force {vi viva)." He, therefore, applied the term "irri- 

 tability" to that which w^e today refer to as "contractility." 

 On the other hand he applied the term contractility solely to a 

 property possessed by other living and dead animal as well as 

 vegetable matter, elasticity, that is, the capability to resume its 

 original form after distortion. He makes a sharp distinction 

 between "irritability," which manifests itself by a contraction of 

 the muscles after stimulation by its own vital force {vi viva), 

 and the "sensitivity," which is possessed only by the nervous 



1 Alhrecht v. Haller: "Elementa Physiologiae corporis humani." Tomus IV. 

 Lausanna M D C L XVI. 



