CONVERSION OF CHEMICAL ENERGY 81 



Whatever explanation is found for the accumulation of 

 potassium in cells may be applied to explain the differences in 

 other ions. 



Although Hober has found that the contents of cells show 

 an electrical conductivity * we do not know which substances 

 are the conducting materials. On the other hand Moore and 

 Roaf have hsemolysed red blood corpuscles, dialysed them 

 for forty-eight hours and they found that haemolysis and 

 dialysis do not remove all the inorganic salts from red 

 blood corpuscles, f 



EFFECT OF CHANGES IN THE SURROUNDING MEDIUM ox 

 CELLULAR ACTIVITY 



Under usual conditions it is necessary that any substance 

 that is to exert an effect on cellular activity must reach the 

 cells through their surrounding media. There is no difficulty 

 in the case of those substances that can enter the cells, but 

 there are substances which affect the activity of cells but do 

 not themselves enter the cells. 



The observations of Warburg on sea-urchin eggs stained 

 with neutral red show that the cell contents are acid to this 

 indicator. On putting the eggs into dilute ammonium 

 hydroxide the cell contents become alkaline without an 

 increase in the rate of oxidation but in dilute sodium or 

 potassium hydroxides the cell contents remain acid, yet the 

 rate of oxidation is increased. { 



Thus we see that it is possible to influence the activity of 

 cells by substances that apparently do not enter into the cells. 



The above outline of the interaction of cell surroundings 

 on cells leads to a discussion of the deductions to be drawn 

 from the experimental results and these hinge mainly on 

 whether the cells are or are not surrounded by a semi- 

 permeable membrane. 



The doctrine that cells are surrounded by semi-permeable 

 membranes was at one time widely accepted aiid the membrane 

 was said to be of fat-like material because those substances 

 which affected the activity of cells are all soluble in fats. 



Although many facts agree with the supposition that cells 

 possess semi-permeable membranes there are some facts which 



* R. Hober, Arch. f. d. ges. Physiol., 1910, vol. 133, p. 237 ; 1912, 

 vol. 148, p. 189. 



f B. Moore and H. E. Roaf, Biochem. Journ., 1908, vol. 3, p. 55. 



J O. Warburg, Zeit. physiol. Chem., 1910, vol. 66, p. 305. 



Overton, Studien uber die Narkose; Jena, 1901; H. Meyer, Arch, 

 f. exper. Path, und Pharm., 1899, vol. 42, p. 109. 

 6 



