42 DYNAMICS OF LIVING MATTER 



most plant cells a condition ultimately arises in which the protoplasm 

 becomes separated from the cellulose wall, the so-called plasmolysis. 

 Nevertheless it cannot be said that plant cells are impermeable for 

 salts, inasmuch as the building up of the living matter of the plant 

 depends upon the diffusion of certain salts from the soil into the plant, 

 e.g. nitrates, phosphates, sulphates, potassium salts, etc. For the 

 animal cell this can be demonstrated still more strikingly. The com- 

 mon striped muscle of the heart loses its excitability rather rapidly 

 when put into a physiological salt solution to which a certain (but not 

 too small) amount of KC1 is added; but if the muscle is taken out in 

 time and put back into a pure NaCl solution, its excitability returns. 

 The velocity with which the inhibiting effect of the potassium salts 

 upon the irritability occurs, depends upon the concentration of the 

 potassium salts in this solution; it is therefore certain that the potas- 

 sium salts diffuse comparatively rapidly into the muscle and out of it. 

 The same can be shown for Na, Ca, and many other, if not all salts. 

 When the muscle is put into an isotonic solution of any sodium salt, 

 rhythmical contractions begin, and the sooner the higher the concen- 

 tration of the sodium salts. The same is true for solutions of barium 

 salts. The velocity with which the sodium salts produce these twitch- 

 ings varies with the nature of the anion of the salt. If to the solution 

 of the sodium salt a small but definite quantity of a calcium salt be 

 added, these contractions are suppressed. These facts are only con- 

 ceivable if we assume that muscle cells are permeable for Na, Ca, and 

 Ba salts, or ions. They must, however, be permeable for other salts 

 also, e.g. Li, Cs, and Rd salts, as they begin to twitch in these solu- 

 tions.* The more toxic salts, e.g. those of the heavy metals, must also 

 be able to diffuse into the cells, as otherwise they could not be so 

 toxic. 



The salts diffuse more slowly into the muscle than water. If mus- 

 cles be put into salt solutions of various concentrations, it will be ob- 

 served that during the first hour or hours, the muscle absorbs water 

 and swells in hypotonic solutions, while it loses water in hypertonic 

 solutions. This phenomenon is, in wide limits, independent of the 

 nature of the salt in solution. f If the muscle remains longer in the solu- 

 tion, however, the influence of the osmotic pressure diminishes, and the 

 specific effects of the salt appear. I found that in a 0.7 per cent solu- 

 tion of NaCl, or an equivalent solution of NaBr or Nal, a muscle does 

 not materially change its weight during eighteen hours. If there is 



* Loeb, Festschrift fur Professor Pick, 1899. Pfluger's Archiv, Vol. 91, p. 248, 1902. 

 See also the numerous papers of Ringer in this field of investigation. 



f Loeb, Fftiiger's Archiv, Vol. 69, p. I, 1897; and E. Cooke, Jour, of Physiology, Vol. 

 23, p. 137, 1898. 



