2O8 GENERAL BIOLOGY OF MICRO-ORGANISMS 



CeHVCOOH, reacts with other chemicals the reaction takes 

 place at the reactive group, or side-chain, rather than in the 

 nucleus. The graphic formula may illustrate this point better. 



H 



I 

 H C O 



\ /\ II 

 C C C OH 



I 

 H C C 



\/ \ 

 C H 



H 



The six carbon atoms in the ring are stable, and a strong chem- 

 ical reagent, such as phosphorus pentachloride, reacts with the 

 side-chain without attacking the ring. So in the living cell, 

 Ehrich assumes, as a working hypothesis, the existence of a 

 wonderfully complex but comparatively stable chemical nucleus, 

 with abundant and various more reactive side-chains. These 

 latter serve to combine with food materials in the surrounding 

 lymph, and these are then utilized in the cell by an intramo- 

 lecular rearrangement of atoms which is always in progress. Use- 

 less atomic groups formed in the metabolism of the cell are de- 

 tached and passed off as excretions. These reactions of intra- 

 molecular rearrangement and molecular disintegration also 

 find their analogues in carbocyclic chemistry. 



Antitoxins. Von Behring and Kitasato (1890-91) showed 

 that animals injected with small non-fatal doses of toxin of the 

 tetanus bacillus, produce as a result of this treatment a some- 

 thing which circulates in solution in the blood plasma, which 

 is capable of neutralizing the poisonous properties of the tetanus 

 toxin. Soon afterward von Behring obtained analogous results 

 with the toxin of diphtheria. The protective substances in the 

 blood were called antitoxins. The exact chemical composition 



