234 CHEMISTRY OF PLANT LIFE 



irregular contractions of a voluntary muscle or with the rhythmic 

 contractions of a heart muscle. 



By means of such investigations as those just mentioned, it 

 has been found that the part of the protoplasm which is most 

 active is always electro-negative to the part which is less so; that 

 is, the electric current flows from the more active to the less active 

 portion of the protoplasm. 



Many different explanations of the origin of the electric 

 current which develops when the protoplasm is stimulated into 

 activity have been suggested; but none of them have, as yet, any 

 experimental confirmation. The most that can be said is that 

 whenever any stimulus excites the protoplasm into activity, there 

 is instantly developed in it an electrical disturbance, which con- 

 tinues as long as the action is in progress. Recent investigations, 

 which have shown that there is a direct relation between many of 

 the vital processes of protoplasm and the ratio of the electrolytes 

 which it contains, particularly the ratio of sodium and potassium 

 to calcium, would seem to indicate that the development of the 

 electrical disturbance is a direct result of variations in the pro- 

 portions of the salts of these metals, either brought about by, or 

 themselves causing, changes in the permeability of the protoplasm, 

 following the stimulus which determines the nature of the activity 

 which it is to undergo. But there is as yet no indication concern- 

 ing the mechanism by which this stimulation, with its resultant 

 electrical phenomena, is transmitted to the protoplasm and accom- 

 plishes its characteristic effects. 



ACIDITY OR ALKALINITY OF PROTOPLASM 



The preceding sections of this chapter have dealt almost 

 exclusively with the physical properties of protoplasm; including 

 the phenomena of solution, ionization, surface boundary effects, 

 and electrical disturbances, and their probable effects upon the 

 chemical reactions which constitute its biological activities. It is 

 necessary now to consider another phase of the physical chemistry 

 of protoplasm, namely, its chemical reaction, whether acid, alka- 

 line, or neutral, the effects of variation of this condition upon the 

 activity of the protoplasm, and the mechanism by which it tends 

 to preserve its own proper reaction in this respect. 



The earlier methods of investigation of the chemical reac- 



