CHEMICAL IRRITANTS. 255 



muscular nerves. The following reasons may also be 

 given for the probability of the independent irritability 

 of muscle-substance. A nerve is, as is known, strongly 

 excited by short, sudden variations of a current, and an 

 unpoisoned muscle behaves in the same way; but a 

 muscle poisoned with curare is less sensitive to current 

 shocks of short duration than to such as take place 

 more slowly. If we ascribe independent irritability 

 to muscle-substance, then greater sluggishness prevails 

 in muscle-substance than in nerve-substance, so that 

 the irritating influences require longer time to take 

 effect in the former. In the case of nerves it has, 

 moreover, been shown that currents which pass at right 

 angles to the longitudinal direction of the nerve-fibre 

 are entirely ineffective. In muscles under the influence 

 of curare no difference in this point can be shown. If 

 the independent irritability of muscle-substance is de- 

 nied in spite of this, it must be assumed that in these 

 experiments the point lies in differences between the 

 nerve-fibres and their real ends. But nerves and muscles 

 are evidently very similar, and it might evidently be 

 possible to assume considerable difference between 

 nerve-fibres and nerve-ends, and that these nerve-ends 

 differ from the muscle-substance in nothing but that 

 the power of being irritated is ascribed to the former, 

 while it is denied to the latter. It appears then, that 

 the whole dispute resolves itself into an empty word- 

 strife as to whether this thing which lies between the 

 nerve-fibres and the muscle-substance is to be reckoned 

 as part of the nerve or as part of the muscle. 



7. The much-discussed question of the independent 

 irritability of muscle-substance is, as appears from what 

 has now been said, due principally to the fact that the 



