GENERAL PHYSIOLOGY. 



81 



by a contraction on both the make and break of the 

 ascending current, one comes to a strength of current 

 which causes a contraction on both make and break 

 of both descending and ascending current. This is 

 the medium strength for the preparation and the con- 

 dition in question. 



(4) Let the current be increased still further and by 

 larger increments. After passing another transitional 

 stage one finally reaches a strength of current which 

 causes a contraction on make of descending current 

 and break of ascending current. This is the strong 

 current for the preparation under observation. 



It not infrequently happens that through overstim- 

 ulation and fatigue of muscle the whole experiment 

 cannot be completed upon one preparation except by 

 increasing the current by larger increments. 



(5) Pfliiger's law of contraction may be expressed in the 

 following table: 



(6) But how shall we account for these results? 



Let us recall some of the laws which have been dem- 

 onstrated. 



Law I. The influence of make and break stimulation. 

 The make contraction starts at the kathode and the break 

 contraction starts at the anode. Further, kathodic or make 

 contractions may be caused by a current which is too weak to 

 cause anodic or break contractions. 



