590 STUDIES IN GENERAL PHYSIOLOGY 



loids has to be maintained. This requires certain ions in 

 definite proportions, either Na, K, and Ca (or other combi- 

 nations, for instance Mg and Ca). Distilled water is a poison 

 for the eggs of Arbacia. Hence, if Na be one of the ions of 

 the surrounding solution, Ca and K ions are likewise required. 



My results differ somewhat from those obtained by 

 Herbst. 1 But I pointed out in my last paper that Herbst 

 was misled by his method. 2 This method consisted in 

 making a solution of the same complication as the sea- 

 water, in which, however, one constituent was omitted. In 

 case the eggs did not develop in such a solution, this was 

 considered a proof that the constituent omitted was neces- 

 sary for the development of the eggs. My experiments 

 show that this conclusion is not correct. It is quite possible 

 that the substance which was omitted or removed was not 

 directly necessary for the egg, but only indirectly, inasmuch 

 as it served to counteract the poisonous effects of another 

 constituent of the solution. 



It seems to me that rny experiments necessitate the intro- 

 duction of a new conception, namely, that of physiologically 

 balanced salt solutions. By this I mean salt solutions which 

 contain such ions and in such proportions as completely to 

 annihilate the poisonous effects which each constituent would 

 have if it were alone in solution. Sea-water and blood (and 

 approximately a mixture of 96 c.c. -| NaCl + 2 c.c. l -/ n 

 CaCl 3 +2 c.c, |-n KC1) are physiologically balanced salt 

 solutions. 



It will be necessary to investigate how far the conclusions 

 of pharmacologists, botanists, and bacteriologists concerning 

 the effects of various salts require a correction on the basis 

 of these new facts and conceptions. Their consideration 

 might even prove of use in problems of immunity and 

 adaptation. 



i HERBST, loc. cit., Vol. V (1897), p. 649. 2p ar t II, p. 559. 



