BACTERIACE^E : THE BACILLUS OF DIPHTHERIA 



289 



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 grad- 

 ually deteriorates even at low tem- 

 peratures. Its chemical nature is 

 unknown. 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 

 combine with antitoxin and being 

 relatively stable, the other bearing 

 the poisonous properties and readily 

 undergoing disintegration. The 

 former he has called the haptopho- 

 rous group and the latter the toxo- 

 phorous group. In toxoid the toxo- 

 phorous group has degenerated. 



Diphtheria was recognized as a 

 distinct disease by Bretonneau in 

 1821. It is characterized by a local 

 inflammation, usually on the mu- 

 cous membrane of the throat, the 

 nose, more rarely the genital mu- 

 cous membrane, or the surface of 

 a wound, and by an accompanying 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 be only a mild reddening or it may be a wide- 

 spread area of necrosis. Most frequently there is an exudate 



I 9 



FIG. 121. B. diphtheria, culture 

 on glycerine agar. 



