x] of the Nervous System. 293 



"me, but they will I hope do so when they are willing to 

 "distinguish the contractile force common to all animal fibre 

 " from the irritable force proper to muscle alone. I also 

 " shewed that that force was something perpetually living, and 

 " that it often broke out into movement though no external 

 " stimulus such as could be recognized by us was acting. By a 

 1 ' stimulus, however, it could at any time be called back from 

 'rest into action. In a movement produced through it I 

 "distinguished between the stimulus which might be very 

 " slight, and the movement called forth by the stimulus which 

 " might be very powerful." 



" Some," says he, " have wished to call this force the vital 

 " force, but this does not quite please rne since the force may 

 " for some little time survive the life of the body. Hence I 

 "prefer to call it the force inherent in or proper to muscle." 

 He then goes on: 



" Besides this force inherent in muscular fibre, another force 

 " is exercised in it, so far like the former in that it alone has its 

 " seat in muscular fibre. But it is different from the inherent 

 "force in as much as it comes from without and is carried to 

 " the muscles from the brain by the nerves, it is the power by 

 "which muscles are called into action." This he calls the 

 vis nervosa. It too survives the death of the body, and in 

 cold-blooded animals is of the same constancy as the inherent 

 force, so that in such an animal recently killed, in which no 

 sensation or voluntary movement remains, a muscle, provided it 

 be moist and whole, is thrown into convulsions when its nerve 

 is irritated. And the same is true of warm-blooded animals. 



Having thus cleared the way by adopting the conception 

 that the movements of the body are the manifestations of 

 this inherent contractile power of muscle, the vis insita, 

 which may develop itself spontaneously, but which is usually 

 brought into play by the instrumentality of the nerves, by the 

 vis nervosa, Haller was able, in his remarkable chapter, " On 

 the Phenomena of the living Brain," to deal in a true scientific 

 spirit, indeed in a modern spirit, with the many and difficult 

 problems of the nervous system. 



He first confines himself to what can be learnt from 



