120 Chapter V 



gelatine much better than does the serum of the same animals. From 

 the experiments of Tchistovitch (I.e. supra p. 110) on rabbits that 

 have been immunised against eel's ichthyotoxin, it must be accepted 

 that the red corpuscles of these animals are often very sensitive to 

 the action of the poison at a period when the blood serum of the 

 same rabbits exhibits a marked antihaemotoxic power. It is not 

 until later in the process of immunisation, when the serum loses a 

 great part of this power, that the red corpuscles become resistant to 

 the ichthyotoxin. 



But before we abandon the hypothesis of the production of anti- 

 haemotoxins by the red corpuscles we must see if it cannot be 

 reconciled with the facts, by the application of Ehrlich's side-chain 

 [128] theory 1 . This theory was evolved with the object of explaining the 

 production of antitoxins and their action on bacterial and vegetable 

 toxins. Later, Ehrlich has extended it to the cytotoxins, anticyto- 

 toxins and bactericidal substances. 



According to Ehrlich the complex molecule of albuminoid sub- 

 stances contains, besides the central stable nucleus, a number of 

 side-chains, or "receptors," which fulfil various accessory functions 

 and serve especially for the nutrition of the cell. These receptors 

 have a great affinity for the various substances necessary for the main- 

 tenance of the life of the cell. Under normal conditions these receptors 

 seize nutritive molecules, as a leaf of Dionaea seizes the fly that 

 serves it as food. Under special conditions these receptors lay hold 

 of complex molecules of albuminoid substances, such as the various 

 toxins. In this case the receptor, instead of combining with a molecule 

 which supports life, fixes a molecule which poisons the cell. Accord- 

 ing to Ehrlich's theory on the constitution of toxins their molecules 

 contain an atomic group which poisons the toxophore, and another 

 group which combines with the receptor the haptophore. The toxic 

 group of a complex poison, such as ichthyotoxin, cannot penetrate into 

 a red corpuscle except by the help of the haptophore group and of the 

 corresponding receptor. When a red corpuscle has absorbed a large 

 number of molecules of ichthyotoxin, the united action of the toxo- 

 phore groups renders life impossible and the corpuscle is dissolved. 

 But when a red corpuscle has been touched by only a few toxic 

 molecules, too few to compromise life, there is merely immobilisation 



1 Klin. Jahrb., Jena, 1 897, Bd. vi, S. 299 ; " Croonian Lecture," Proc. Roy. Soc. Lon- 

 don, 1900,Vol.Lxvr,p.424. Ehrlich, Lazarus u.Pincus, "Leukaemie,etc."inNothnagel's 

 Specielle Pathologie u. Therapie, Wien, 1901, Bd. vm, Schlussbetrachtungen, S. 163. 



