voi...x] Bancroft. Esterly. — Physiological Polarization. 109 



11:07 — Cut branchial side loop in half. Small central loop is 

 contracting, but the direction cannot be made out. 

 The other two pieces are contracting ah-branchially. 



11:14 — All three pieces are now clearly contracting in the 



original ab-branchial direction. 

 1:46 — All contractions have stopped. 



In some cases the pieces tailed t utract and immersion in 



the sodium chloride solution was necessary before the direction 

 of the heart-heat could be recorded. Contractions were obtained 

 from insolated pieces of 5] hearts experimented upon in this way; 

 and in 41 (or 80 per cent.) of them all the isolated pieces that 

 contracted at all did so in the direction they had before being 

 isolated. From some of these hearts as many as four or five 

 pieces all contracting in the fixed direction* and unconnected 

 with either end were obtained. From the ten hearts that did not 

 behave normally many isolated pieces that contracted in the 

 direction of fixation were also obtained. But as in all of these 

 hearts at least one piece did not follow the normal law they were 

 considered as furnishing evidence against polarization. How- 

 ever, in spite ot this method of estimating the evidence which is 

 decidedly unfavorable to our theory, still the preponderance of 

 evidence in favor of polarization is too large to have been due to 

 accident. 



It seemed possible, however, that the persistence of the fixed 

 direction after isolation of the pieces might not be due to a change 

 in the heart tissues, but that the result might have been caused by 

 a tendency for the pieces always to beat in the direction away from 

 the most recent cut. which could then he isidercil as the stim- 

 ulus controlling tin- direction of the contractions. 



The most convincing type of experiment bearing on this 

 question consisted in first removing' one end of the heart to allow 

 the direction of the contractions to become fixed. Then the sec- 

 ond end was also removed, and a long loop connected with neither 

 end and pulsating in the direction of fixation was obtained. 

 Five or six small pi s were now cut from the end of the loop 



* By contraction in the fixed direction or the direction of fixation we mean the 

 direction of the contractions when tin- part of the heart in question was connected 

 with only one of the ends of the heart 



