INOCULATIONS WITH B. DIPHTHERIA. 291 



pretation for this process, viz.: that it is due to the pro- 

 duction of a soluble poison by the bacteria growing at 

 the seat of inoculation, which, gaining access to the cir- 

 culation, produces the changes that we observe in the 

 tissues of the internal viscera. 



This poison has been isolated from cultures of the 

 bacillus diphtherioB, and is found to belong, not to the 

 crystallizable ptomaines, but to the toxic albumins — 

 bodies which, in their chemical composition, are anal- 

 ogous to the poison of certain venomous serpents. 

 By the introduction of this toxalbumin, as it is called, 

 into the tissues of guinea-pigs and rabbits, the same 

 pathological alterations may be produced that we have 

 seen to follow the result of inoculation with the bacilli 

 themselves, except, perhaps, the production of false 

 membrane. 



Under certain circumstances with which we are not 

 acquainted the bacillus diphthericB becomes diminished 

 in virulence or may lose it entirely, so that it is no 

 longer capable of producing death of susceptible ani- 

 mals, but may cause only a transient local reaction 

 from which the animal entirely recovers. Sometimes 

 this reaction is so slight as to be overlooked, and again 

 careful search may fail to reveal evidence of any reac- 

 tion at all. The production of the extremes of its 

 pathogenic properties, viz., death of the animal, on the 

 one hand, and only very slight local effects on the other, 

 were at one time thought to indicate the existence of two 

 separate and distinct organisms that were alike in cultural 

 and morphological peculiarities, but which differed in 

 their disease-producing power. Further studies on this 

 point have, however, shown that the genuine bacillus 

 dvphihericB may possess almost all grades in the degree 



