Physiological "Polarity" and Electrical Polarity. 337 



Here we see the cut end with a higher potential than the surface, 

 except at the girdle and in front of the fifteenth segment, where 

 the current is reversed. The worm was small and immature, but 

 as other young worms gave the same sort of readings as the ma- 

 jority of mature worms, the peculiar results cannot be due to im- 

 maturity. In fact, it is difficult even to guess why this worm should 

 give such different responses from the others. Another case 

 was also recorded in which the cross section was anterior and of 

 higher potential than the neighboring surface for a series of seven 

 sections. 



Experiment 4. Lumbricus terrestris. Piece one inch long from 

 near the posterior end of the worm, with a cut surface at each end 

 of the piece. Zero point of galvanometer, 28.6; electrodes, 30.0. 



Electrodes at anterior end and 



middle of piece 26.3 Anterior cut end positive 



Electrodes at posterior end and 



middle of piece 27.1 Surface positive 



Electrodes at both ends 27.0 Anterior cut end p^ositive 



In this experiment the anterior electrode is positive with respect 

 to the posterior one, whether it be on an end or on a surface, and 

 we get a constant direction of current from before backward. The 

 worm from which the piece was cut gave the usual results for 

 the other readings made on it. The piece was cut out by two 

 consecutive cuts with no appreciable time between them, so that 

 the freshness of the cut could not, as it does in other cases given 

 later, influence the result. One other case resembled this one, 

 while two cases showed conditions in which the middle was posi- 

 tive with respect to both ends, and three cases showed conditions 

 in which the middle was negative with respect to both ends. 



It has been stated that marked changes in the distribution of 

 potenial between the surface and cross section often occur at the 

 fifteenth segment and at the girdle region. When a worm is cut 

 in two at the fifteenth segment the cut end has usually a higher 

 potential than the surface either anterior or posterior to it, or when 

 short pieces of a worm are cut with one end at the fifteenth seg- 

 ment, that end is positive to the other, whether it be an anterior 



