540 COLLECTED STUDIES IN IMMUNITY. 



Another possibility of cell immunity is that the protoplasm of 

 cells which are ordinarily susceptible is no longer affected by cer- 

 tain poisons. This kind of immunity, which to be sure I consider 

 very rare, would correspond to mithridatism or acquired tolerance 

 in the old sense. A fourth possibility, finally, is the adaptation of 

 the phagocytic apparatus in Metchnikoff's sense. 



It is obvious, of course, that all the sevarious subordinate kinds 

 of immunity occur alone as well as in manifold combinations. Thus, 

 as already mentioned, immunization with eel blood is followed by 

 antitoxin immunity and tissue immunity. In the lower animals, 

 however, which as Metchnikoff has shown are but little adapted 

 to the production of antitoxin, other defensive contrivances leading 

 to cell immunity will predominate From this point of view there- 

 fore the condition described by Gruber, namely, that frogs can be 

 immunized against abrin without their showing any antitoxin, offers 

 no difficulty. So far as the frog is concerned the only question is 

 which kind of cell immunity is present, i.e., whether there is a dis- 

 appearance of receptors, or whether there are sessile receptors, etc. 1 



In view of the detailed statements given above I presume I need 

 add nothing to the following passage in Gruber's conclusion: 



(?) "The production of antibodies takes place at entirely different 

 localities than does toxic action." 



The discerning reader will at once see that this statement does 

 not in the least contradict my views. In fact it is merely another 

 way of expressing what is really the nucleus of my theory. The 

 generalization, however, is false, that the production of antibody 

 necessarily takes place in localities different from those in which 

 toxic action occurs. If Gruber therefore believes that this riddles 

 my theory it is evident that he understands the principles under- 



1 Gruber cites, as a serious objection to my theory, that Madsen observed 

 immunity in a rabbit which had been immunized with diphtheria toxin, and 

 yet was unable to find antitoxin in the blood. I will only say that Madsen 

 did not find the blood entirely free from antitoxin since he tested the serum 

 only to 1/10 I. E. Small quantities of antitoxin could be very well have been 

 present and these, of course, would be of considerable importance for the ques- 

 tion as to whether this was a case of entire absence of antitoxin. Besides 

 this I may add that in diphtheria poison the case reported by Madsen must 

 be extremely rare. During the course of many years the different Serum 

 Institutes have immunized thousands of different animals against diphtheria. 

 In all this time, however, I have never learned of a case analogous to Madsen's, 

 either from the literature or from private sources. 



