68 CLINICAL BACTERIOLOGY. 



experiments with these substances, Ehrlich recognized that 

 in the process of immunization through the activity of the 

 disease-poisons in the body of the patient, substances are 

 formed that he designates anti-bodies (antitoxins). These 

 are, in a certain sense, antidotes, inasmuch as they neutral- 

 ize or prevent the toxic action of the disease-poisons. 

 When these antitoxins are present in sufficient amount, im- 

 munity exists. In the process of immunization with the aid 

 of bacteria or their poisons (direct, active, immediate immu- 

 nizatioii), the antitoxins are formed either from the bac- 

 terial products themselves, or, under their influence, from 

 substances that exist in the body preformed. 



The disease continues until an adequate amount of anti- 

 toxin has been formed. For this reason the older methods 

 of immunization are effective only after disease of greater or 

 less severity, and after the lapse of a certain time. Immu- 

 nization by means of serum (passive, mediate, indirect im- 

 munizatioii) represents the transmission of preformed anti- 

 toxins. Therefore, this method, on the one hand, induces 

 no disease, and, on the other hand, it establishes immunity 

 at once ; and this is, for the same reason, also, more transi- 

 tory, lasting only a few weeks. 



Whence the antitoxins are derived has not yet been 

 finally determined. The view that the antitoxin is formed 

 directly from the toxin introduced for purposes of immuni- 

 zation appears gradually to be losing ground. It is more 

 probable that in the course of every toxic disease the anti- 

 toxin is produced together with the toxin within the body. 

 The antitoxic activity of the serum is abolished by exposure 

 to a temperature of from 60 (140 F.) to 70 C. (158 F.). 



The manner in which antitoxins act upon the bacterial 

 poisons has not yet been clearly determined. Originally, 

 it was assumed that the antitoxins destroy the bacterial poi- 

 sons. The injection of a mixture of an antitoxin-containing 

 serum and bacterial poison proved innocuous. From this 

 it was concluded that the poison is destroyed by the anti- 

 toxin of the serum. It soon transpired, however, that de- 

 struction of the poison by the antitoxin does not take place, 

 but that, to use the expression of Ehrlich, in the physio- 

 logically neutral mixtures of toxin and antitoxin both sets 

 of constituents are yet present as such. Buchner and 

 Roux assumed an action of the antitoxin upon the cells, as 

 a result of which the latter are rendered immune to the in- 



