818 CONTRACTION-WAVE IN MUSCLE 



dilution with one-half reduction of salts to three-fourths reduction, 

 the propagation-rate falls off more rapidly than the electrical con- 

 ductivity; while if more of the Ringer salts be replaced by sugar 

 the irritability is soon decreased to zero. In the solutions of low 

 electrical conductivity the tissue becomes non-irritable in the course 

 of 2 hours or more, but recovers immediately upon being replaced 

 in Ringer's solution. It is remarkable that increase of oxygen tension 

 may largely compensate for the reduction in salts. If oxygen be 

 bubbled through the solutions the decrease of propagation-velocity 

 may remain almost proportional to the decrease of electrical con- 

 ductivity until only one-twentieth of the salts of Ringer's solution 

 remain {cf. Table V) 



Seventy-four series of experiments have been conducted upon 

 propagation-velocities in varying mixtures of Ringer's solution and 

 isotonic sugar solution. The order of the solutions used has been 

 frequently altered to offset errors; while the time between the trans- 

 fer of the muscle to a given solution and the taking of the record 

 has always been long enough to allow the tissue to reach an equi- 

 librium with the medium. Experim.ents 141, 142, and 143 {cj. Table 

 III) are typical of the observations, and are selected with reference 

 to the mixtures ranging from 30 per cent Ringer's solution to normal 

 Ringer. The velocities and the conductivities are averaged and the 

 ratios calculated in Table IV. In these experiments the mixtures 

 were agitated continuously with a slow stream of air. 



Experiments have been made on the velocity of the contraction- 

 wave in solutions of still lower electrical conductivity, in which an 

 increase of oxygen tension enables transmission to occur. Nine ex- 

 periments in which oxygen was bubbled through the mixtures are 

 recorded in Tables V and VI. In three of these experiments a mix- 

 ture was employed containing only 5 per cent of the normal salt 

 content of Ringer's solution. The muscle contracted and transmitted 

 the contraction wave under these conditions; although in the same 

 solutions containing oxygen at air tension no such behavior appears 

 possible. In pure m/4 sugar solution saturated with oxygen these 

 muscles lost irritability in slightly less than a half hour. Two 

 of the experiments in the 0.05 Ringer's solution show a transmission 

 rate very close to that calculated from the electrical conductivity. 



