70 PHYSICOCHEMICAL BASIS OF PHYSIOLOGICAL PROCESSES 



Biological Processes Depending on Adsorption 



Instances in which adsorption undoubtedly plays a most important 

 part in physiological processes are as follows: 



1. The action of enzymes (see page 71). 



2. The combination of toxin with antitoxin occurs according to the laws 

 of adsorption rather than those of mass action. In this case it is im- 

 portant to note that when the toxin of diphtheria is added in small suc- 

 cessive quantities to diphtheria antitoxin, more toxin is neutralized than 

 when the toxin is all added at once. A similar phenomenon can also be 

 observed by adding filter paper to congo red, more of the pigment being 

 adsorbed when the paper is added in small quantities than when added 

 all at once. The explanation is that relatively more adsorption of a 

 given substance occurs from a dilute than from a strong solution (cf. 

 page 69). 



3. The sensitizing of leucocytes by opsonins, as well as the subsequent 

 ingestion of bacilli by the sensitized leucocytes, both of which follow the 

 course of an adsorption reaction. 



4. The formation of adsorption compounds, such as the inorganic salts 

 and proteins and the complex lecithin compounds that can be extracted 

 from egg yolk or brain tissue. In such compounds the laws of chemical 

 proportion no longer hold, and properties may be exhibited that are quite 

 different from those of either one of its components. When yolk of egg 

 is extracted with ether, for example, a compound of lecithin with vitellin 

 goes into solution, although vitellin itself is quite insoluble in ether.* 

 There can be no doubt that adsorption compounds of this character are 

 very abundant in living cells, and that they are constantly being formed 

 and broken down. 



5. It is possible that the distribution of a substance in protoplasm is 

 largely dependent on the influence which it has on the surface tension 

 at the boundary of different phases in the protoplasm. 



*By mixing solutions of egg albumin, congo red and a dye called fustic in the presence of 

 alum, the colloidal particles of which each is composed run together to form larger colloidal ag- 

 gregates, which by ultramicrosconic examination can be seen to be composed of a red, a yellow 

 and a green colloidal particle. The attractive force holding the particles together is electric in 

 this case. 



