188 THE TOXINS PRODUCED BY BACTERIA 



artificial cultures of these bacteria. In dealing with these it is 

 necessary to distinguish between the effects produced by the 

 actual constituents of the bacterial protoplasm (intracellular 

 toxins) and those which in a few bacteria are traceable to 

 soluble substances passing out into the media in which these 

 bacteria may be growing (extracellular toxins). The former 

 are concerned in the action of by far the greater number of 

 pathogenic bacteria; the latter account for the pathogenic 

 processes originated in a limited number of cases of which 

 diphtheria and tetanus are the most important. This dis- 

 tinction is important as, in consequence of these last two 

 diseases having had much attention directed towards them early 

 in the history of research on the subject, there has hitherto 

 been too much tendency to take for granted that poisons of 

 a similar constitution are concerned in all cases of bacterial 

 intoxication. At present such an assumption is not justified 

 by facts, and we do not even know whether the intracellular 

 and extracellular toxins belong to the same group of chemical 

 bodies. At present, however, the terms are used as a con- 

 venient means of accentuating a difference in solubility between 

 the two groups of toxic bodies. 



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 such organisms as the pyogenic cocci, the 

 b. typhosus, and the v. cholerse likewise give rise to pathogenic 

 effects. Such intracellular toxins may appear in the fluids in 

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

 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 originate 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. 

 It is impossible, at present, to obtain intracellular toxins apart 

 from other derivatives of the bacterial protoplasm, and thus 



