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ELECTRO-PHYSIOLOGY 



CHAP. 



minimal stimulation distance and 1-2 mm., a very small 

 interval of difference. With closer approximation the rhythm 

 always passed into a smooth, unbroken tetanus. Here, again, 

 the difference already pointed out between the muscles of 

 hydrophilus and dytiscus is apparent, since, as we have seen, the 

 former, like the sluggish claw-muscles of the crab, yield longer, 

 rhythmically interrupted tetani, while the frequent rhythmical con- 

 tractions characteristic of dytiscus under the same conditions are 

 nowhere present. We have no hesitation in claiming for these 



a 



FIG. 61. a, Rhythmical contractions of leg of Dytiscus marginal!* with tetanising excitation. 

 Stimulation -frequency, 880 per sec. 1>, Rhythmically interrupted tetani from leg of 

 Hydrophilus piceus. (Sclioenlein.) 



observations of Sclioenlein and Bichet an analogy with the fact 

 that cardiac muscle also yields rhythmical contractions under the 

 same conditions, although, of course, we have in these to reckon be- 

 sides with the value of the single twitches, which is never or rarely 

 the case in beetle muscle. In the quick muscles of dytiscus, in 

 which the frequency of rhythmical contraction varies at an 

 average of 26 per sec., exceptionally rising to 30, it is perhaps 

 legitimate to credit the single contractions with the value of 

 single twitches, while the sluggish hydrophilus and crab muscle 

 throughout exhibit short tetani. AVe shall presently see that 

 cardiac muscle always, and striated skeletal muscle under at 



