ENDOTOXINS 187 



of bacterial intoxication. At present such an assumption is not 

 justified by facts, and we do not even know whether the endo- 

 toxins and exotoxins belong to the same group of chemical 

 bodies. The terms are merely used as a convenient means of 

 accentuating a difference in solubility between the two groups 

 of toxic bodies. 



Endotoxins. — 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. choleree likewise give rise to 

 pathogenic effects. Such toxins may ajjpear 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 during growth bacteria often originate 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 result in liberating endotoxins. It is 

 impossible, at present, to obtain these toxins apart from other 

 derivatives of the bacterial protoplasm. Our knowledge con- 

 cerning their action is chiefly derived from the study of the 

 effects produced by injecting into animals either the bodies of 

 bacteria (killed by chloroform vapour or by heat) or bacterial 

 protoplasm disintegrated mechanically or artificially autolysed. 

 When effects are produced by such injections they do not present 

 in any particular case specific characters. They usually appear 

 very soon, it may be in a few hours after injection of the toxic 

 material ; there is not the definite period of incubation which 

 with other toxins often elapses before symptoms appear. 



Aggressins. — In certain cases there is difficulty in under- 

 standing the action of bacteria which neither form soluble toxins 

 in a fluid medium nor possess a highly toxic protoplasm, and 

 which yet produce effects at a distance from the focus of 

 infection, e.g., b. anthracis. To explain such occurrences it has 

 long been regarded as a possibility that some bacteria are 



