814 



CONTRACTION-WAVE IN MUSCLE 



Most determinations of the propagation-velocities have accordingly 

 been made in mixtures of sea water and sugar solution containing 40 

 per cent or more of the normal electrolyte content; i.e., 0.4 or more 

 sea water. 



Estimates of the velocity of propagation of the contraction-wave 

 in the Limulus heart based upon records taken from the two opposite 

 ends of the organ are variable and inconsistent. Records taken from 

 the second and eighth segments also appear in no cases to have given 

 consistent results. If recording devices are attached to the second, 



TABLE I. 

 Contraction-Wave in Limulus Heart. Experiment 30. Sea Water, 21°C. 



fourth and eighth segments as recorded in Table I, the records show 

 that at times the contraction of the second segment may actually 

 precede that of the eighth, while the intermediate segment may 

 contract before either of the others. Hence the time elapsing be- 

 tween the contractions at opposite ends of the heart may be so brief 

 as to show that the case is not one of simple transmission of a single 

 contraction-wave from end to end of the organ. Transmission, how- 

 ever appears to be uniform over a short region near the middle of the 

 heart. Records from this middle region, i.e., fourth, fifth, and sixth 

 segments, indicate that these segments contract almost simultaneously. 



