ii CHANGE OF FORM IN MUSCLE DURING ACTIVITY 155 



spreads over the fibres in both directions from the point excited, 

 lasting as a rule a little longer than the excitation. Under 

 these , conditions there can be no question of referring the 

 phenomenon to diminished muscular excitability. It appears 

 indeed from Milrad's (15) experiments upon muscles of which 

 the excitability had been raised or depressed by different chemical 

 substances (veratrin, chloroform, NaJOO g , caffein) that the 

 appearance of the idio-muscular swelling is favoured by diminution 

 of excitability, and delayed by its augmentation, provided the 

 difference between the normal and the poisoned, or fatigued, muscle 

 is insignificant, and does not often exceed the error of observa- 

 tion, but that the slow undulatory contractions are only apparent 

 with normal or increased excitability. Both Schiff and Auerbach 

 state that the play of waves on stroking with a blunt needle 

 appears only in the muscles of freshly-caught frogs, and Milrad 

 says that this form of contraction may nearly always be produced 

 if excitability is artificially heightened, or abolished if it is lowered. 

 Since both the idio-muscular swelling and the wave-action may 

 be observed in curarised animals, they are obviously the con- 

 sequence of direct muscular excitation, although on many sides 

 the theory has been put forward (chiefly on the ground of totally 

 inadequate experiments, 16) that the motor nerve-endings take 

 part in the muscle phenomenon under discussion. 



Although mechanical stimuli are undoubtedly the most favour- 

 able to the production of the idio-muscular swelling, the applica- 

 tion of other stimuli is by no means excluded. Auerbach, e.g. (I.e. 

 p. 342), found that with local application of "weak" faradisation 

 currents a lump was raised at either pole, while with stronger 

 currents there was a marked swelling over the whole intra- 

 polar area, as was afterwards confirmed by Milrad (I.e. p. 266). 

 And further, we must regard the persistent closure contraction 

 (infra) which appears at the kathode on sending in a constant 

 current of sufficient strength in both striated and smooth muscle, 

 as an idio-muscular swelling, while the wave of striated muscle 

 (Hermann's galvanic wave), that may be seen to proceed from 

 the anode under similar conditions, seems to be directly com- 

 parable with the wave-action on mechanical excitation. 



As Eollett (7, p. 201 ff.) correctly pointed out, the muscles of 

 insects must have an especial significance re interpretation of 

 relations between the contraction wave and the manifestations 



