826 CONTRACTION-WAVE IN MUSCLE 



possible that sugar might have some direct toxic action upon the 

 tissues. Later considerations, however, make this doubtful. In the 

 first place the parallelism between the electrical conductivity and 

 propagation rate is closer with higher than with lower tensions of 

 oxygen, although the sugar solutions are of the same concentration. 

 In the second place if sugar acts toxically the toxic effect should in- 

 crease proportionately to the increase in the length of exposure to 

 the more concentrated sugar solutions. That this is not the case is 

 indicated by the fact that the frog and Limulus tissues after immer- 

 sion in pure sugar solution for periods up to 3 and 4 hours recover 

 thfeir irritability, upon return to Ringer's solution, just as rapidly 

 and completely as when exposed to the pure sugar solution for periods 

 just sufficient to abolish irritability. A further peculiarity in the 

 action of sugar solutions, namely, the marked difference between the 

 time required for loss of irritability in sugar solutions and for recovery 

 of irritability on return to the normal conducting solution — the lat- 

 ter interval being many times shorter than the former — is not readily 

 explained. It is beyond the aim of the present paper to discuss 

 this problem, and it may be that the conditions must be more care- 

 fully investigated. 



The author desires to thank Dr. Ralph S. Lillie for constant help 

 and advice in the study of the present problem, and the Trustees 

 of Clark University for the arrangements under which the research 

 has been prosecuted. 



