436 



SCIENCE 



[N. S. Vol. XXXVII. No. 951 



float for three days, before they begin to 

 shrink and fall to the bottom. This and 

 similar experiments show that the specific 

 semi-permeability of an animal membrane 

 is influenced by the nature of the solutions 

 to which it is exposed. In physiologically 

 balanced solutions, e. g., NaCl + KCl + 

 CaCla in the proportion in which these 

 salts exist in the sea-water, this specific 

 semi-permeability is preserved longest, if 

 not permanently. In solutions of one salt 

 only the permeability is as a rule increased 

 as soon as the concentration of the salt in 

 the solution exceeds a certain limit. This 

 limit varies for different salts and varies 

 also for the same salt in different animals. 

 This is the reason why a pure NaCl solu- 

 tion becomes injurious more rapidly to one 

 form of organism than to another. The 

 reader will notice that in this field of phe- 

 nomena the chemical nature of the solution 

 is of primary importance. 



This dependence of the preservation of 

 semi-permeability upon the chemical na- 

 ture of the surrounding solution suggests 

 the possibility of a chemical interaction 

 between cell walls and surrounding solu- 

 tion in which the chemical and physical 

 properties of the semi-permeable wall are 

 modified. 



VII. THE DIPFERENCE IN THE MODE OF 



ABSORPTION OP WATER IN LIVING 



AND DEAD CELLS 



We may conclude from the preceding 

 data that the salts of the surrounding solu- 

 tion react chemically with the colloids of 

 the surface of the cell and that the prod- 

 ucts thereby formed determine the degree 

 of permeability or impermeability of the 

 cell walls. 



These changes vary with the chemical 

 nature of the salt. In some solutions the 

 permeability is preserved much longer 

 than in others. Thus the muscle keeps its 



normal function much longer in a NaCl or 

 a LiCl solution than in a solution of KCl 

 or CaClj. As long as the muscle is irri- 

 table or even some time after it ceases to 

 be irritable it obeys Avogadro's law in the 

 solutions of pure salts. After 18 hours, 

 however, the muscle is killed in pure iso- 

 tonic solutions of KCl as well as of CaCL, 

 while it is still alive in solutions of NaCl 

 and LiCl. At that time it continues to 

 obey the law of Avogadro in NaCl and 

 LiCl, but no longer in KCl and CaCl„. 



CHANGE IN WEIGHT OP A GASTROCNEMIUS OF A 



FROG AFTER IS HOURS IN SOLUTIONS EQUI- 



MOLECULAR WITH m/8 NaCl " 



While the muscle undergoes no, or only 

 slight, changes in weight in the isotonic 

 solutions of Na and Li salts it absorbs a 

 considerable amount of water in KCl, loses 

 water in CaCl2. 



Overton, who later repeated and con- 

 firmed these results, explained them on the 

 assumption that the normal muscle is per- 

 meable for KCl, but not for the other salts. 

 In a pure KCl solution the salt gradually 

 enters the muscle, whereby the osmotic 

 pressure of the muscle is increased and the 

 latter swells; while in a CaCL solution the 

 KCl naturally contained in the muscle 

 leaves the muscle and the diminution of 

 the number of molecules in the muscle 

 makes the surrounding originally isotonic 

 solution hypertonic for the muscle. One 

 fails to see, on such an assumption, why 

 the muscle does not also lose water in a 

 NaCl solution. It has been demonstrated 



=>LK)eb, Pfluger's Archiv, Vol. 75, p. 304, 1899; 

 "Studies in General Physiology," Vol. II., p. 511, 

 Chicago, 1906. 



