vol.3.j Bancroft, Esterly. — Physiological Polarization. Ill 



Secondly, it' the direction, in which an isolated piece of the 

 hear! beats, depends upon the fact that previous to isolation 

 one end had contracted before the other and consequent^ 

 had recovered its excitability more completely; then, if the 

 heart could be made to slop beating for a short time, the excita- 

 bility of the two ends would soon become equalized, and there 

 should be no relation between the direction of contraction before 

 and after isolation. Accordingly, to test this explanation, our 

 records of experiments in which pieces stopped after isolation 

 and then started again when brought into the sodium chloride 

 solution were gone over. They showed that after a quiescent 

 period of from 3 to 90 minutes, 13 of the 14 pieces experimented 

 upon contracted in the direction they had before immersion in 

 the salt solution. Since the quiescent interval in these experi- 

 ments was very much longer than the normal interval between 

 contractions, the results, in spite of their small number, make it 

 very improbable that the differential recovery of the two ends of 

 the pieces from the lowered excitability following each contrac- 

 tion is the cause of the fixed direction of the contractions in 

 isolated pieces of the Ciona heart. 



As neither of the two possibilities considered accounts for the 

 phenomena, we are forced to conclude that connection with only 

 one end of the heart brines about a change of some kind in the 



tissues as the piece s mnected continues after isolation to beat 



in the previous direction. This change may be termed a physio- 

 logical polarization, but whether it is caused by the long eon- 

 tinned constant direction of the contractions or the connection 

 with one end only, apart from the direction of the contractions, 

 we cannot say. So far as we know similar cases of polarization 

 have not been described. 



DEVIATIONS FROM NORMAL BEHAVIOR. 



Occasionally the normal behavior of the heart, which presented 

 strong evidence in favor of polarization, was replaced b.\ con- 

 tractions of the most varied kind, which will he briefly described. 



Pulsations from both ends <<t I he same time, which have been 

 seen by both Loe'li and Schultze, were observed in two of seveu 

 Cionas, in which puncturing the body wall had exposed the 



