98 Dr. A. P. W. Philip on the 



posed that the power of the muscular fibre was derived from 

 the nervous system, which was regarded as the general source 

 of power in the animal body ; and, many circumstances seem 

 at first view to countenance this opinion. When the nerves are 

 divided, the muscles of voluntary motion can no longer be 

 excited by the will, and when the power of the brain and spinal 

 marrow is destroyed, that of the muscles never long survives. 

 In like manner if a limb be removed from the rest of the body, 

 all its powers soon cease. 



It was taught by Haller, however, that the power of mus- 

 cles resides in themselves, and is only lost when the influence 

 of the nervous system is withdrawn, in consequence of the 

 failure of other powers, and that this influence acts merely 

 as a stimulus to the muscles, and that only with respect 

 to those of voluntary motion, those of involuntary motion 

 being excited by other means. He thus explains phenomena 

 which appeared inexplicable on the suppositions of his pre- 

 decessors. 



I shall here give a translation, a little abridged, of what is 

 so well said on the state of our knowledge of this subject in 

 the report of the Royal Academy of Sciences, on the experi- 

 ments of M. Le Gallois. 



" The theories ofBoerhaave and Stahl reigned almost alone, 

 when, in 1752, Haller published his experiments on irritability. 

 These experiments and those of his followers tend to prove, 

 that the contractile power belongs essentially to the muscular 

 fibre. That property which Haller sometimes speaks of under 

 the name of vis insiia, sometimes after Glisson under that of 

 irritability, is the source of all the motions which take place in 

 the animal, but it cannot produce them except some cause, 

 some stimulus determines it to act. Thus, all muscular motion 

 implies two things, the irritability which produces the con- 

 traction of the muscle, and the stimulus which determines the 

 irritability to act. The irritability is everywhere the same. 

 It only varies in intensity in the different muscles, but it does 

 not obey the same stimuli in all the muscles. The nervous 

 power is the natural stimulus to all those which are under the 



