vol. 3.] Bancroft, Esterly. — Physiological Polarization. 1 * » T 



evidence forthe conclusion that these ganglia arc connected with 

 the brain. 



EXPERIMENTS. 



The experiments here described were carried on al the San 

 Pedro laboratory of the University of California during the 

 summers of 1901 and 1902. They were almost entirely the work 

 of the junior author, and were concerned, almost exclusively, 

 especially in the second summer's work, with the problem of the 

 physiological polarization of the Ciona heart, and not with the 

 general question of the Tunicate heart-beat. For very kindly 

 assistance and advice in connection with preparing the results 

 for publication we wish to express our thanks to Professor Loeb. 



Ciona intestinalis was the only species used: the hear) being 

 examined in sea water unless the contrarj is slated. Pieces of 

 the heart were separated from one another principally bj cut- 

 ting. When tied they gave in general the same results; but 

 although no case of contractions passinga ligature was observed, 

 isolation by tying was avoided on account of the possibility of 

 such a passage. 



Ordinarily (in 148 out of 253 pieces) we found that pieces of 

 the heart not connected with either end contracted spontaneously, 

 and frequently these contractions began immediately after isola- 

 tion. In other cases it was found that they began only after a 

 variable quiescent interval. When pieces isolated in this way 

 failed to contract automatically, contractions could almost inva- 

 riably be started by immersion in a one per cent, sodium chloride 

 solution. Equimolecular solutions of potassium chloride and 

 calcium chloride had no such effect. Comparing these results 

 with those of Lingle and Schultze on the automaticity of pieces 

 of the heart, it will be seen that different species, and even the 

 same species at different places, may differ in this respect. This 

 difference need not surprise us when we remember the variability 



of living beings in general. It may be due to the presei of 



ganglion cells in the central part of the heart in some species, or 

 to some other characteristic of the tissues which would make 

 them less sensitive to the action of the constituents of the sea 

 water that tend to inhibit automatic contractions. 



