BACTERIAL POISONS 159 



abundantly, could take up only a minimal amount of substance. But if 

 metatrophic ferment or putrefactive bacteria invade the body they would 

 break up not merely their own bulk of organic substance, but a hundred or 

 a thousand times as much. As a secondary aggravating effect, such changes 

 must not be overlooked in bacterial infections ; they may, for instance, 

 cause destruction of tissue. 



Bacteria may, from purely physical reasons, cause local disturbances 

 of the circulation by accumulating in the capillaries. This happens in 

 anthrax, where the vessels are for short distances completely plugged by 

 the bacilli. 



These effects of bacterial intrusion, to which formerly great importance 

 was attached, are now looked upon as merely subsidiary phenomena. The 

 violent symptoms and serious consequences of a bacterial infection are now 

 known to be due to the action of toxines, poisons produced by the micro- 

 organisms. 



The contagium animatnm that invades the body from outside produces 

 in the tissues the virus inanimum, the lifeless poison. The investigation of 

 these poisons is now in full progress, but, as may be readily conceived, is 

 attended by great difficulty, for they are all of them extremely unstable 

 bodies, and many are of proteid nature, and therefore less accessible to the 

 ordinary methods of chemical research. It is certain that they include 

 substances of very various chemical composition. 



The oldest known group is that of the ptomaines or putrefactive alka- 

 loids, so called on account of the resemblance of their chemical reactions to 

 those of vegetable alkaloids. They play, however, only a very small part 

 in the toxic action of pathogenic bacteria. The isolation of the actual 

 specific toxines (142) from the cultures has been attended with but little 

 success as yet, in spite of the great amount of labour that has been spent 

 upon the subject, and we speak of the ' toxines ' without really knowing 

 them in a pure state. But to have them chemically pure, although very 

 desirable, is not absolutely necessary, as the following description shows. 

 To separate the poisons dissolved in the culture fluids from the bacteria, 

 it is sufficient to filter bouillon cultures through porous earthenware 

 or kieselguhr. If the poisonous filtrate thus obtained, for instance from 

 tetanus cultures, be injected into animals, they die with the same sym- 

 ptoms of lock-jaw as if they had been injected with the bacilli themselves. 

 In the same way the filtrate of diphtheria cultures kills the animal with 

 the symptoms of diphtheria. In short, it has been shown that all patho- 

 genic bacteria produce soluble poisons, that these poisons alone are able to 

 give rise to the disease, the nature and course of which depend solely upon 

 the nature of the toxines. Old cultures in particular contain large quanti- 

 ties of toxines ; they are highly ' poisonous,' whilst the younger growths are 

 distinguished by the more rapid growth of the micro-organisms they are 



