ELECTROKINETICS 381 



lized, fertilized, and cleaving Arbacia eggs to be negative 

 under all conditions, the potential being of the order of 

 30 mv. 



If it is actually true that certain cells are positively charged 

 under normal conditions, then one of two conclusions is unavoid- 

 able: either the cell is not covered with a protein; or, if a protein, 

 it is a very unusual one, in that its isoelectric point, in terms of 

 pH, is above that of most proteins and on the alkaline side of the 

 usual pH value of physiological solutions. Most proteins form 

 salts in which the protein ion is the anion (negative) above a pH 

 of 4.0 or 4.5. The pH value of physiological solutions is 5.5 to 

 7.4. A protein with an isoelectric point in this range is rare; 

 and that is where the isoelectric point of proteins that cover 

 positively charged cells would have to be. The coating on cells 

 need not, of course, be protein, though there are many reasons to 

 believe that it usually is (see page 375). 



While it is not likely that plants differ from animals or that 

 groups or strains of organisms differ from each other in the sign of 

 the charge of their cells, it does appear that genera, species, and 

 pathological strains of plants and animals differ very character- 

 istically in the magnitude of the potential on their cells and 

 particularly in their isoelectric points; in other words, the poten- 

 tial on living cells appears to bear a definite relationship to cer- 

 tain biologic (generic and pathogenic) properties. 



Abramson found that the rate of migration of red blood cor- 

 puscles in an electric field was greatest in the dog and least in the 

 rabbit. He obtained the following order: dog > rat > mouse, 

 cat > monkey > man > guinea pig > opossum > pig > sloth > 

 rabbit. The corpuscles of the dog migrate the fastest and there- 

 fore have the highest electric potential. 



Bacteria probably require an electric charge in order to remain 

 in suspension and therefore to keep alive. It appears from work 

 by S. Miidd that their potential also aids them in their penetra- 

 tion of mammalian membranes and therefore in their passage 

 from cell to cell. It might then be asked. Does electric potential 

 determine pathogenicity; is the virulence of bacteria in any way 

 associated with their surface potential? A definite answer to this 

 question cannot be given. Virulence, as we know it, is a very 

 complex property, but the pathogenicity and the electric potential 

 of bacteria have apparently been correlated in at least one case. 



