488 



E. J. LUND 



and removal of the P.D. can be brought about by this anaesthetic. 

 The complete investigation of the effect of anaesthetics upon the 

 P.D. will be left for later consideration. The purpose of the 

 previous experiments is simply to furnish a conclusive demon- 

 stration of two facts: 1) A normal difference of electrical poten- 

 tial exists along the stem of Obelia. 2) This potential difference 

 is associated with the living condition of the tissue of the stem. 



TABLE 5 



A represents a series of tests on apical pieces of the main stems of five different colo- 

 nies. B represents a series of tests on the corresponding basal pieces of the stems 

 of the same colonies. The lengths of apical and basal pieces of the same stem are 

 equal. Note that the potential differences in the apical and basal pieces are oppo- 

 site in direction 



THE DIRECTION AND MAGNITUDE OF THE FALL OF ELECTRICAL 

 POTENTIAL ALONG THE STEM 



Because of the nature of the method used in the preceding and 

 following experiments, it should be clear that the results are not 

 what would be desired in a quantitative investigation of this 

 problem. But, nevertheless, as will be indicated in the following 

 two experiments, some idea may be gained of the magnitude and 

 direction of the fall of electrical potential along the stem by 

 comparing the magnitude of the differences in deflection produced 

 by apical and basal halves or quarters of the same stem. 



