ELECTROLYTES IN LIVING MATTER 75 



Strongylocentrotus purpuratus, are similar.* NaCl, KC1, and CaCl 2 

 are necessary: as without one of these salts no segmentation is pos- 

 sible. For the complete development Mg and SO 4 are also required, 

 but these latter two constituents do not possess the same degree of 

 importance as Ca, Na, or K. In addition, a substance is needed which 

 keeps the solution neutral, e.g. NaHCO 3 . Other constituents of the 

 sea water, such as PO 4 , Fe, are not required. This latter statement 

 disagrees with the conclusions of Herbst. f 



The same is true for Medusae : they will keep alive in solutions of 

 NaCl, KC1, CaCL,, MgCl 2 , in the proportion and concentration in 

 which these solutions occur in the sea water. In addition, a substance 

 is required which keeps the sea water neutral, e.g. NaHCO 3 . I think 

 these examples may suffice as the proof of the fact that for marine 

 animals NaCl and CaCL, and KC1 are essential for the maintenance 

 of life. It is questionable whether the substances which growing 

 animals require for the manufacture of living matter are taken from 

 the surrounding solution. Were this the case, only traces of any of 

 these salts should be sufficient, while in reality the proportion of Na, 

 K, and Ca can vary only within certain limits in the solution. 



The tissues of marine animals seem to require a solution of the 

 same character. Dr. Rogers has, at my suggestion, determined in 

 which solution the heart of a marine crab beats longest. He found 

 that sea water is an excellent "nutritive" solution for the heart, and 

 that the same is true for a van't Hoff solution; namely, a solution of 

 100 molecules NaCl, 2.2 KC1, 2 CaCl 2 , 7.8 MgCl 2 , 3.8 MgSO 4 . To this 

 should be added a trace of NaHCO 3 . The action of sea water becomes 

 better if a little CaCL, is added, possibly on account of a slight antago- 

 nistic effect between Ca and Mg. 



It is remarkable that the tissues of fresh-water and land animals, 

 e.g. the frog, the tortoise, and apparently the mammals, live longest 

 in a solution which has the same constitution as the sea water, and 

 differs from the latter only in its concentration. The optimal concen- 

 tration of the solutions for frogs and land animals is about that of a 



Wl 



Q- solution of NaCl. In order to keep the isolated heart of cold-blooded 



o 



animals alive, Ringer has recommended the following solution : J 



* Loeb, Pfliiger's Arehiv, Vol. 103, p. 503, 1904. 



t Herbst, Arehiv fitr Entivickehitigsmechanik, Vol. 5, p. 649, 1897, and numerous other 

 papers on the same subject. 



Herbst did not recognize the antagonistic effects of salts, and so concluded that if the 

 elimination of one of the constituents of the sea water was injurious, this proved the neces- 

 sity of the omitted substance for the animal. The above-mentioned observations on Fundu- 

 lus show in m.y opinion the fallacy of this conclusion. 



t Quoted after Rusch, P/Higer's Arehiv, Vol. 73, p. 535, 1898. 



