308 BACTERIOLOGY. 



the cellular elements of the internal organs there is but 

 one interpretation for this process, viz., that it is due to 

 the production of a soluble poison by the bacteria grow- 

 ing at the seat of inoculation, which, gaining access to 

 the circulation, produces the changes that we observe in 

 the tissues of the internal viscera. 



This poison has been isolated from cultures of the 

 bacillus diphtherias, 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 path- 

 ological alterations may be produced that we have 

 seen to follow the result of inoculation with the bacilli 

 themselves, except, perhaps, the production of false mem- 

 brane. 



Under the influence of certain circumstances with which 

 we are not acquainted the bacillus diphtherias becomes dim- 

 inished 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 care- 

 ful search may fail to reveal evidence of any reaction 

 at all. This exhibition of the extremes of its patho- 

 genic properties, viz., death of the animal, on the one 

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

 was 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 



