lOO PROTOPLASMIC ACTION AND NERVOUS ACTION 



special interest as indicating the importance of electrical 

 factors in the structural stability of the protoplasmic 

 surface layer, and suggests a reason why depolarizing 

 influences have in general a stimulating action on irritable 

 cells. The relations between structural change and 

 stimulation will be considered in more detail later. 



Hober and Kozawa^ found this isoelectric point to 

 vary for different species of corpuscles and to be char- 

 acteristic for a particular species; i.e., certain corpuscles 

 are more readily made positive than others by H ions 

 and polyvalent ions; thus the corpuscles of rabbits and 

 guinea pigs were found to require the least H-ion con- 

 centration for reversal and those of the ox and pig the 

 highest; those of the dog, cat, goat, and man were 

 intermediate. 



Animal Isoelectric Point (PH) 



Rabbit Between 3.8 and 3.4 



Guinea pig ca. 3.4 



Man (and cat) ca. 3.13 



Dog Between 3.13 and 2.98 



Sheep Between 2.98 and 2.77 



Pig ca. 2.77 



The relative order with La ions was the same. Such 

 differences are to be referred to the specific peculiarities 

 of structure, composition, or permeability characteristic 

 of each kind of corpuscle. 



In their general or common features, these phe- 

 nomena indicate that the behavior of the protoplasmic 

 free surface with reference to the ions present in the 

 medium resembles that of the surface of an individual 

 oil-droplet in an emulsion. It may be assumed that 



^ Hober and Kozawa, Biochem. Zeitschrift, LX (1914), 146. 



