iv ELECTROMOTIVE ACTION IN MUSCLE 419 



most unfavourable cases the process excitatory of secondary con- 

 traction is propagated at a velocity of 25 cm. per sec., i.e. very 

 slowly, the velocity in other cases is so great that the methods 

 employed (by which velocities at 2 m. per sec. can be estimated) 

 were unable to determine it. It appeared even from Bernstein's 

 first experiment that the velocity of the wave of electrical variation 

 in muscle is extremely fluctuating, and diminishes with comparative 

 rapidity in the excised muscle. If the period of the contraction 

 wave is any guide to that of the wave of variation, we might 

 recall the well-known waves of contraction, visible to the eye on 

 account of their slowness, which appear more particularly in insect 

 muscle, but also under some conditions in the freshest frog's 

 muscle, e.g., as above, in the sartorius or adductor magnus, 

 when mechanically excited with the point of a needle (Kiihne, 

 I.e. p. 36 f.), or as the galvanic wave, with strong battery 

 currents. 



With regard to the question, which section of the electrical 

 wave of variation is most important in secondary excitation, we 

 should a priori be disposed to choose the foremost, i.e. the 

 steepest, as most efficient. In any case it is as follows from 

 the evidence given above a very short segment of the excitatory 

 wave which excites the nerve resting upon it. 



In all effective nerve-excitation (more particularly electrical) 

 a certain rapidity of time distribution is implied in the changes 

 set up by the stimulus ; and this appears in secondary excitation 

 from muscle to nerve also, since sluggishly-moving muscles are 

 for the most part unfitted to produce secondary excitation in 

 frog's nerve. 



Matteucci stated that the secondary contraction failed when 

 he applied the frog's sciatic nerve to the excited muscular mass 

 of the intestine, stomach, or bladder. Kiihne confirmed the same 

 in the highly mobile ureter of the rabbit ; nor could he discover 

 secondary action in the striated muscles of Hydrophilus and 

 Astacus, even when, in the latter, the primary contraction of the 

 adductor claw-muscle was produced by excitation of the nerve. 

 So again the intestine of the tench, which, at the part where there 

 are striated muscles, contracts tolerably rapidly, and almost 

 twitches, with electrical excitation. Ktihne also found total 

 absence of secondary action in the muscles of Emys europcea, 

 both in the pale musculi retrahentes capitis collique and the red 



