162 THE TOXINS PRODUCED BY BACTERIA 



The introduction of the principle of rendering fluid cultures 

 bacteria-free by nitration through unglazed porcelain, and its 

 application by Roux and Yersin to obtain, in the case of the 

 b. diphtheriae, a solution containing a toxin which reproduced 

 the symptoms of this disease (vide Chap. XV.), encouraged the 

 further inquiry as to the nature of this toxin. An attempt on 

 the part of Brieger and Fraenkel to obtain a purified diphtheria 

 toxin by precipitating bouillon cultures by alcohol (the product 

 being denominated a toxalbumin) did not greatly advance know- 

 ledge on the subject, and further investigation soon showed that 

 characteristic toxins can be isolated from but few bacteria. 



General Facts regarding Bacterial Toxins. The following 

 may be regarded as the chief facts regarding bacterial toxins 

 which have been revealed by the study, partly of the bodily 

 tissues of animals infected by the bacteria concerned, partly of 

 artificial cultures of .these bacteria. The dead bodies of certain 

 bacteria have been found to be very toxic. When, for instance, 

 tubercle bacilli are killed by heat and injected into the body 

 tissues of a susceptible animal tubercular nodules are found 

 to develop round the sites where they have lodged. From 

 this it is inferred that they must have contained characteristic 

 toxins, seeing that characteristic lesions result. The bodies 

 of the cholera vibrio are likewise toxic. Such intracellular 

 toxins, as they have been called, may appear in the fluids 

 in which the bacteria are living (1) by excretion in an un- 

 altered or altered condition, (2) by the disintegration of the 

 bodies of the organisms which we know are always dying 

 in any bacterial growth. The death of bacteria occurs also 

 in the body of an infected animal, and the disintegration of 

 these dead bacteria constitutes an important means by which 

 the poisons they contain are absorbed. There is some evidence 

 that often bacteria produce during growth poisons which 

 are hurtful to their own vitality, and also that ferments 

 are produced by them which have a solvent effect on the 

 poisoned members of the colony. Such a process of autolysis, 

 as it has been called, may have an important effect in 

 liberating intracellular toxins. We do not, however, under- 

 stand all that takes place under such circumstances ; for the 

 dead bodies of many bacteria, such as those of anthrax and 

 diphtheria, are relatively non-toxic. As it is impossible, at 

 present, to obtain intracellular toxins apart from other deriva- 

 tives of the bacterial protoplasm, all our knowledge concerning 

 their effects is derived from the study of what happens when the 

 bodies of bacteria killed by chloroform vapour or by heat are 



