ELECTROLYTES IN LIVING MATTER 97 



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Similar conditions exist for the development of the eggs of a 



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sea urchin, Arbacia. I found that in neutral solutions of NaCl, KC1, 

 CaCl 2 , MgCl 2 , MgSO 4 , the eggs of Arbacia can reach the pluteus stage, 

 but that no normal skeletons are formed. If, however, NaHCO 3 is 

 added, normal skeletons are formed. Similar results were previously 

 obtained by Herbst, and in this case also the NaHCO 3 serves for the 

 neutralization of an acid. Experiments in Strongylocentrotus purpura- 

 tus were still more surprising in this respect.* When these eggs were 

 put immediately after fertilization into a van't Hoff solution (100 NaCl, 



2 KC1, 2 CaCl 2 , 7.8 MgCl 2 , 3.8 MgSO 4 ), only few eggs went beyond the 

 two-cell stage, and only very few reached the pluteus stage. If, however, 

 to 100 c.c. of such a solution 0.5 to i.o c.c. f m NaHCO 3 were added, 

 almost all the eggs went into the pluteus stage. In such a solution the 

 development also occurred just as fast as in normal sea water. 



The addition of o.i c.c. f m Na 2 CO 3 solution caused also some eggs 

 to reach the pluteus stage. These plutei, however, did not live as long 



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as when the bicarbonate was added. When 0.2 to 0.4 NaHO was 



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added to 100 c.c. of the van't Hoff solution, the majority developed, but 

 no skeletons were formed. We must, however, take into consideration 

 the fact that in such solutions, as I found, NaHO is neutralized in a few 

 hours or in less than a day by the CO 2 of the air and the CO 2 formed 

 by the eggs, while the formation of a skeleton occurs only after from 



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 forty-eight to seventy-two hours. The addition of 0.8 c.c. of a 



Na 2 HPO 4 solution acted similarly to the addition of NaHO. 



I think these examples may suffice to show the importance of a 

 regulator which is capable of keeping the solution in which marine 

 animals live neutral. The same is true for the liquids in which tissues 

 live; this point was investigated by Rogers in experiments on the heart 

 of the crab. Here, also, the addition of bicarbonate made a great differ- 

 ence. This is also, as I believe, the explanation of the fact that Ringer's 

 solution is improved through the addition of a trace of NaHCO 3 . Gaule f 

 was the first to point out the necessity of neutralizing the acid formed in 

 the heart if we wish to make it beat in an artificial solution. In fresh- 

 water animals, Wolfgang Ostwald made the interesting observation that, 

 if Gammarus be put into a salt solution of a comparatively high osmotic 

 pressure, life could be prolonged considerably by adding NaHCO 3 

 to the solution. He was able to show that without the addition of the 



* Loeb, Pftiiger's Archiv, Vol. 103, p. 503, 1904. 

 t Gaule, Du Bois-Reymond*s Archiv, p. 291, 1878. 



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