242 PHARMACEUTICAL BACTERIOLOGY 



index stated by a decimal figure. The index thus obtained indicates the 

 relative phagocytic power of the individual's blood tested, whether below 

 or above the normal, or normal. 



The opsonic index taken in the various chronic forms of bacterial infec- 

 tions is invariably below normal and shows that the phagocytic power is 

 low, and it seems to prove that the chronicity is due to the subnormal 

 phagocytosis. The injection of several millions of devitalized bacteria of 

 the kind causing the infection, induces the formation of the specific 

 opsonin, arouses the phagocytic activity and corrects the pathologic 

 condition. The opsonic method of treatment has been extensively tested 

 through the use of specifically active bacterial suspensions (vaccines, 

 bacterins or opsonogens) which in some instances have g*iven excellent 

 results. It has also been found that substances other than opsonins*may 

 increase phagocytosis, as for example, nucleinic acid and collargol. 



From the foregoing it becomes evident that immunity from disease 

 depends upon the presence in the body of antitoxins, bacterolysins, and the 

 opsonins which induce phagocytosis. It is furthermore possible to increase 

 the activity of these agents artificially. All three agents are specific hi 

 nature as already stated. Ehrlich has attempted to explain the phenomena 

 of immunity according to his receptor or side chain theory (Seitenketten- 

 theorie). This theory, which is rather complex and highly technical, was 

 first used to explain cell metabolism. Hinman's version of the side chain 

 theory is very simple and we give it as follows: As applied to immunity 

 the basis of the theory is the conception of the duplex nature of antigens. 

 An antigen is a substance, of bacterial or other origin, which has the power 

 when introduced into^ the body, of inducing the formation of specific anti- 

 bodies. Not all toxins or poisons have this power. For example, strych- 

 nin and the toxin of tetanus produce similar physiologic effects, but only 

 the latter is capable of producing an antibody. Ehrlich explains this 

 difference by assuming that strychnin and most other vegetable poisons 

 enter into a loose combination with the cell plasm, analogous to an aniline 

 dye which can be readily dissolved out again; whereas the toxin is firmly 

 bound to the cell, representing in a measure a toxic food-stuff in chemical 

 union with and assimilated by the cell. The atomic combination of 

 the toxin antigen, which represents this chemical union is designated 

 the haptophore group, while the atomic combination of the cell-plasm 

 with which the haptophore group unites is called the cell receptor group. 

 The haptophore group is distinct from the atomic group which produces 

 the toxic or pathologic effects, designated as the toxophore group. These 

 two groups of the antigen (toxin), namely the haptophore group and 

 the toxophore group, act independently of each other and possess different 

 properties. The toxophore group is easily destroyed by heat (60 to 65 C.) 



