MEMBRANES AND CELL-PROCESSES 151 



puscles of the frog by passing induction-shocks ; and I find that the rate 

 of formation of this compound through intracellular oxidation can be 

 greatly accelerated by this means, especially in leucocytes, where the 

 oxidation-rate is relatively rapid. I am inclined, therefore, to attribute 

 to the variations in the electrical polarization of the membranes an 

 important general role in varying the rate and possibly the character 

 of the energy-yielding intracellular oxidations. On this view, intra- 

 cellular metabolism would be largely controlled by membrane-processes. 

 How this is possible may be illustrated by the case of anesthesia just 

 discussed. The ether-impregnated plasma-membrane is relatively un- 

 affected, as compared with the normal membrane, by isotonic sodium 

 chloride solution; and consequently the stimulation, with its resultant 

 increase in oxidation, is prevented by thus altering the membrane. 

 The precise nature of the conditions in these and similar phenomena 

 can be elucidated only by further study. 



I had hoped to discuss the role of membrane-processes in other cell- 

 activities, such as fertilization, cell-division and development, but the 

 space at my disposal is insufficient. Before closing, however, I wish to 

 refer briefly to the large class of physiological processes in which a 

 regular rhythmical repetition of the same change, e. g., contraction, is 

 the essential characteristic. Such processes include ciliary activity, the 

 action of contractile vacuoles, the action of the heart and of nerve-cells 

 like those of the respiratory center or the heart-ganglia of certain ani- 

 mals. In the division of cells during early development, a definite 

 though slower rhythm is also seen. Now an electrical rhythm accom- 

 panies the physiological rhythm in muscle and nerve cells, probably in 

 cilia, and almost certainly in dividing cells, as indicated by the experi- 

 ments of Miss Hyde on dividing fish-eggs. The existence of a chem- 

 ical rhythm — of carbon dioxide production — has been demonstrated in 

 dividing cells (sea-urchin eggs) by Dr. Lyon, and we may infer its 

 presence in the other rhythmical processes. The electrical rhythm indi- 

 cates a rhythm of changing permeability, and of this there is some 

 direct evidence in dividing egg cells. In all of these cases we have to do 

 with automatic processes whose rhythm proceeds of its own accord, 

 provided the external conditions remain normal. Each cycle in the 

 rhythm furnishes itself the conditions for its own recurrence. The 

 question arises : from what physico-chemical point of view is it best to 

 regard this class of phenomena ? In the case of a rhythmical contractile 

 tissue three interdependent and synchronous rhythms may be distin- 

 guished — a chemical, a mechanical (presumably the expression of sur- 

 face-tension changes), and an electrical. An elementary model of 

 these phenomena is, I believe, furnished by the experiments of Bredig 

 and his pupils on the rhythmical catalytic decomposition of hydrogen 

 peroxide in contact with metallic mercury. When a ten per cent, solu- 



