FACTS REGARDING BACTERIAL TOXINS 163 



injected into animals. When effects are produced by such 

 injections they do not present in any particular case specific 

 characters. They are of the nature of general disturbances of 

 metabolism, as manifested by fever, loss of weight, etc., often of 

 such serious degree as to result in death. It is important to 

 note that when pathogenic effects are produced these 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. 



Sometimes the media in which bacteria are growing become 

 extremely toxic. This is more marked in some cases than in 

 others. The two best examples of bacteria thus producing 

 soluble toxins are the diphtheria and tetanus bacilli. In these 

 and similar cases when bouillon cultures are filtered bacterium- 

 free by means of a porcelain filter, toxic fluids are obtained, 

 which on injection into animals reproduce the highly character- 

 istic symptoms of the corresponding diseases. In the case of 

 the b. anthracis and of many others, at any rate when grow- 

 ing in artificial media, such toxin production is much less 

 marked, a filtered bouillon culture being relatively non-toxic. 

 Poisons appearing in culture media have been called extra- 

 cellular toxins, but we cannot as yet say whether they are 

 excreted by the bacteria or whether they are produced by 

 the bacteria acting on the constituents of the media. We 

 therefore cannot as yet draw a hard and fast line between 

 intra- and extracellular toxins, but the terms are convenient, 

 and may apply to two actually different sets of bodies. That 

 the poisonous capacities of a bacterium may be very compli- 

 cated is shown by what is known in the case of the cholera 

 vibrio, where the poisons which dissolve out into the culture 

 fluid are probably different in their nature from those which act 

 when the dead bacteria are injected into an animal. The extra- 

 cellular toxins are the more easily obtainable in large quantities, 

 and it is their nature and effects which are best known. No 

 method, however, has been discovered of obtaining them in a 

 pure form, and our knowledge of their properties is exclusively 

 derived from the study of the toxic filtrates of bouillon cultures 

 these filtrates being usually referred to simply as the toxins. 

 These toxins differ in their effects from the intracellular poisons 

 in that specific actions on certain tissues are often manifested. 

 Thus the toxins of the diphtheria, the tetanus, and the botu- 

 lismus bacilli all act on the nervous system ; with some of the 

 pyogenic bacteria, on the other hand, poisons, probably of 

 similar nature, produce solution of red blood corpuscles (this 



