ELECTROLYTES IN LIVING MATTER 89 



or into 10 c.c. | m CaCl^ + 50 c.c. distilled water, the center usually 

 begins to beat rhythmically. The rhythmical contractions may last 

 for three hours or more. Such rhythmical contractions can even be 

 caused in a center which has been washed and kept for three hours in a 

 pure solution of cane sugar, to make sure that the sea water at the surface 

 of the muscle cells has been entirely removed. In this case, however, 

 the contractions do not last as long, inasmuch as a solution of cane 

 sugar as well as a pure CaCl^ solution are injurious to the muscle. 



BaClj is much more effective than CaClj, as it requires a much lower 

 concentration of BaCl^ than of CaClj to produce rhythmical contractions 

 in an isolated center of Polyorchis. Even in a solution of J c.c. f m 

 BaCl^ + 50 c.c. f m cane sugar, rhythmical contractions were produced 

 which lasted about nine minutes. SrCl^ is much less toxic than BaClj 

 and it acts more like CaCl^. 



If it be true that the exchange of Ca for Na or K, or vice versa, in 

 certain organic combinations be the cause of these rhythmical contrac- 

 tions, we are apparently confronted with conflicting facts ; namely, 

 that Ca-salts, as well as salts which precipitate Ca, produce rhyth- 

 mical contractions; but the facts are no more in conflict in this case 

 than in the similar case of the coagulation of milk, where both a previous 

 treatment of the milk with decalcifying salts or acid, as well as the 

 addition of a soluble calcium salt, favor coagulation. In this case the 

 probable explanation, according to Loevenhart, is that a soluble calcium 

 salt is necessary for the coagulation. This calcium salt may be added 

 from without, or may be obtained from the milk itself, by freeing it from 

 a combination in which it is held there. The same may be true for the 

 rhythmical contractions in the center of Polyorchis. In order that a 

 contraction may occur, the formation of a certain calcium compound 

 (soap or a calcium proteid ?) is required. This condition may be satis- 

 fied by the diffusion of calcium into the cells from without, or by cal- 

 cium being freed from certain other compounds within the muscle cells 

 themselves (by acid, certain salts, like the oxalates or citrates or, as we 

 shall see later, by the action of enzymes). The process of contraction 

 is due to the substitution of Na or K for the Ca, or vice versa. Ba 

 and Sr act like Ca. 



Why is it that the isolated center of Polyorchis does not contract 

 rh3rthmically in normal sea water? If CaCL, acts as a stimulus, it is 

 not probable that it is the CaCl^ of the sea water which inhibits its 

 contraction. It might be possible that the action of the CaCl^ in. the 

 sea water is antagonized by the NaCl. There seems to be indeed a 

 certain antagonism, inasmuch as it is easier to produce rhythmical 

 contractions in a pure solution of CaCL, or in a solution of CaCl, in cane 



