302 



SPECIFIC MICRO-ORGANISMS 



even 0.5 c.c. or more may be required to kill a guinea-pig, and 

 some strains of bacilli morphologically indistinguishable from 

 B. diphtheria seem to produce no toxin at all. The toxin is 



quickly destroyed by boiling and 

 loses 95 per cent of its strength in 

 five minutes at 75° C. It gradually 

 deteriorates even at low tempera-- 

 tures. Its chemical nature is' un- 

 known. Ehrlich has shown that old 

 toxin which has lost much of its 

 poisonous property is still able to 

 combine with as much antitoxin as 

 before. This deteriorated toxin is 

 called toxoid. He explains the phe- 

 nomenon by assuming the existence 

 of two distinct chemical groups in the 

 toxin molecule, one serving to com- 

 bine with antitoxin and being rela- 

 tively stable, the other bearing the 

 poisonous properties and readily un- 

 dergoing disintegration. The former 

 he has called the haptophorous group 

 and the latter the toxophorous 

 group. In toxoid the toxophorous 

 group has degenerated. 



Diphtheria was recognized as a 

 distinct disease by Bretonneau in 

 1 82 1. It is characterized by a local 

 inflammation, usually on the mucous 

 membrane of the throat, the nose, 

 more rarely the genital mucous 

 membrane, or the surface of a wound, and by an accompany- 

 ing general intoxication giving rise to focal necrosis in various 

 parenchymatous organs and affecting more particularly the 

 heart and the nervous system. The local inflammation may 



Pig. 124. — B. diphtheria, culture 

 on glycerine agar. 



