98 DYNAMICS OF LIVING MATTER 



bicarbonate, the hypertonic solution was rendered acid by the 

 animals.* 



During some of the above-mentioned experiments Osterhout and I 

 found that marine algae under the influence of light make the sea water 

 slightly alkaline, while in the dark they do not act in this way. They 

 produce also this alkalinity under the influence of light in a solution of 

 NaCl, KC1, CaCl 2 , which shows that the act of assimilation is accom- 

 panied by the excretion of a base. It is possible that this is one of the 

 means by which the reaction of the ocean is kept neutral in spite of the 

 animal life. It is also possible that this is one of the reasons why ani- 

 mals keep better in a well-lighted aquarium if green plants are added. 



Acids as well as alkalis act as poisons in comparatively low concen- 

 trations. The toxic concentration for acids is generally much smaller 

 than for bases; the toxic effects are not altogether in proportion to the 

 concentration of the H- or HO- ions. Organic acids as a rule are more 

 toxic than should be expected from their degree of dissociation. A very 

 weak base like NH 4 OH is for Gammarus (possibly for many organisms) 

 more toxic than NaHO, while tetramethylammonium hydroxide is 

 less toxic.f This indicates that in the case of ammonia the NH 3 is 

 responsible for the toxic effects, and not the HO- ion. This is supported 

 by the fact that NH 4 C1 is more toxic for animals than NaCl, and almost 

 as, if not slightly more toxic than KC1. By way of digression I may 

 remark that, contrary to a possibility I had considered for some time, I 

 have reached the conclusion that the toxic effects of electrolytes are 

 determined by chemical reactions and equilibrium conditions, and not by 

 the electric charges of the ions. 



4. ELECTRICAL STIMULATION 



In plants, electrical stimulation plays no r61e, and the same may 

 be said to be true for those phenomena in the life of animals which they 

 share with plants, e.g. cell division. From all we know cell division 

 cannot be called forth or controlled by the galvanic current; but the 

 galvanic current is an excellent stimulant for the functions of those 

 tissues which may be considered characteristic of animals alone; 

 namely, muscles and nerves. It is perhaps more than a mere acci- 

 dent that in this respect the efficiency of Na- or K- and Ca-salts and 

 the electrical current coincide. 



We have seen in the third lecture that the solid parts of living tissue 

 consist of colloids which are nonconductors, while the liquids are col- 



* Wolfgang Ostwald, PflugeSs Archiv, Vol. 106, p. 568, 1905. 

 t Not yet published. 



