TOXIN AND ANTITOXIN. 539 



of experimental analysis, and not by high-flown words of a mis- 

 leading dialectic. 



(d) "Cell immunity can be acquired without the formation of 

 antibodies." 



This statement, too, does not surprise me. All that the side- 

 chain theory aims to do is to explain how the production of anti- 

 bodies may be conceived. But I have never yet claimed that this 

 is the only means by which the organism can defend itself against 

 deleterious influences. I would call attention particularly to the 

 Sixth Communication on Hsemolysins, 1 in which Morgenroth and I 

 pointed out that not all substances capable of being anchored need 

 necessarily excite the production of antibodies. We have always 

 emphasized, however, that immunity may be developed despite 

 this, chiefly through a disappearance of receptors. 2 In our isolysin 

 experiments we observed that the blood-cells became insusceptible 

 and we demonstrated that this was due to a lack of receptors. The 

 interesting fact observed by Kossel and by Camus and Gley that 

 during the course of immunization with eel blood, the blood-cells 

 of rabbits acquire a high resistance against that poison, is probably 

 most easily explained by assuming that the cells acquired immunity 

 in the way above mentioned. 



This, of course, does not exhaust the possibilities of the origin 

 of immunity not due to antitoxins. Thus under the influence of 

 the anchored poison new receptors may be formed which are so firmly 

 united to the protoplasm that they are not thrust off. Such receptors 

 Morgenroth and I have therefore termed "sessile receptors." If 

 the product ion of such an excess of receptors takes place in a rather 

 indifferent tissue, as in connective tissue, it will readily be seen how 

 the receptors can serve to deflect the poison, and produce a more 

 or less marked immunity. In that case on comparing a normal 

 animal with an immunized one, the conditions would be like those 

 observed with tetanus poison in normal guinea-pigs and normal 

 rabbits, respectively. The studies of Donitz and Roux have shown 

 that the guinea-pig possesses receptors for tetanus toxin only in 

 the brain, whereas, rabbits, in addition to the receptors in the cen- 

 tral nervous system, possess about thirty times as many such recep- 

 tors outside this system. 



1 See page 88. 



2 Schlussbetrachtungen in Nothnagel's Handbuch., Vol. VIII. 



