l62 MANUAL OF BACTERIOLOGY. 



bacterial products in an extremely marked manner. In tetanus 

 the local wound may be trifling, and in itself utterly incapable 

 of giving rise to the violent muscular spasms from which the 

 patient suffers in consequence of the powerful poison which 

 the tetanus bacillus forms at the point of infection. In diph- 

 theria, although the condition in the throat may be one of severe 

 inflammation, it is of itself insufficient to explain the profound 

 prostration and other symptoms of general poisoning which 

 the case manifests. 



Bacterial poisons are diffused through the culture-medium 

 or they may be retained in the bodies of the bacteria. Con- 

 sequently, they are classed as extracellular and intracellular. 

 In cultures of the diphtheria and of the tetanus bacilli the cul- 

 ture-medium contains the poison, and injections of the broth 

 in which these organisms have been grown produces these 

 diseases just as promptly and effectually as injections of the 

 bacteria themselves. Even when the bacteria is these cultures 

 are entirely removed by filtration through porcelain filters, the 

 filtrate reproduces the diseases with all their symptoms just 

 as characteristically as the unfiltered cultures. On the other 

 hand, in certain bacteria the poisons are contained in the bodies 

 of the bacteria, and are not liberated into the culture-medium. 

 They are only set free by breaking up the cells, either mechani- 

 cally, by grinding in a mortar, or by disintegration in some other 

 way. The disintegration of these bacteria in the animal body 

 is probably the way in which certain of them cause disease. 

 Typhoid bacilli and cholera spirilla probably act in this way. 



The first bacterial poisons to be studied thoroughly were 

 those called ptomaines. Observing the poisonous effects 

 which follow the injection into animals of certain ptomaines 

 derived from bacterial cultures, it was suggested that similar 

 ptomaines, formed by the action of bacteria in the living 

 body, might account for the symptoms of many of the infectious, 

 diseases. The ptomaines were most readily studied because 



