153 ELECTRO-PHYSIOLOGY CHAP. 



According to Eollett, it appears as though the short waves, in 

 many cases, arise in or near a section, from which inferences 

 may be made as to the significance of the muscle-current, or the 

 chemical changes concomitant with the death of the muscle- 

 substance, as a discharging excitation. In individual cases the 

 end-plate can undoubtedly constitute the point of departure for 

 a wave of contraction, and this apparently applies to all the 

 waves developed along one fibre. 



Eollett tried to determine the rate of transmission of these 

 waves in sufficiently long strips of muscle cut out of the extensors 

 and flexors of the hind pair of legs, in large beetles, using the 

 same method which E. H. Weber employed to measure the 

 rapidity of the capillary circulation. The number of metronome 

 beats was counted for the interval between the coincidence of 

 the maximum with a given fraction of the scale, at the beginning, 

 and at the end, of an ocular micrometer. Values were thus 

 obtained of 0'08-0'67 mm. (average, 0'169 mm.); the length 

 of the waves varied between O'OS and 0'115 mm. Thus there 

 are true " miniature waves," which propagate themselves at 

 such a low rate, that even the slowest waves of contraction in 

 striated, vertebrate muscle, varying according to Auerbach 

 from 314 to 371 mm. per sec., have a considerable velocity 

 in comparison. Unfortunately it has till now been found 

 impossible to measure the rate of conductivity of the excitation 

 which provokes the rapid twitch in insect muscles. P>ut it 

 is certain that it must be considerable in twitches of short 

 duration (0-0112-0-527 sees., Eollett), even on Kollett's 

 assumption, that the longest waves (transmitted at greatest 

 velocity) of insects are far behind those of vertebrate muscle. 

 Schiff and others, as we have seen, observed a reflection of the 

 slow contraction wave in many striated, vertebrate muscles, when 

 it reached the end of a fibre. A similar effect seems seldom, if 

 ever, to appear in insects ; Eollett at least has failed to discover, 

 either in the entire muscle of Corethra - larva', or in excised 

 beetle muscle, anything "that could be described as a reflected 

 wave." 



Both in the case (*ttpr) in which the wave arises in the 

 centre of a fibre, and spreads to both sides, and in that where no 

 definite point of departure is to be discovered, it may be seen 

 to disappear suddenly, midway, with no previous diminution. 



