BACTERIOLOGICAL TOXINS AND ANTITOXINS 113 



The action of the endotoxins on the body tissues differs from 

 that of the exotoxins in that they do not give rise to symptoms 

 of a specific character. There is no definite period before 

 symptoms appear, nor do they stimulate the body cells to the 

 production of antitoxin^. Certain protective substances are elabo- 

 rated against them, but they are of a totally different nature to 

 antitoxin. 



Aggressins. In certain cases it is difficult to understand a 

 result of bacterial growth which is due neither to endotoxins nor 

 exotoxins but to some other substance which aids the organisms 

 in combating the body defenses. If, for instance, tuberculous 

 exudate is removed from an animal suffering from the disease, and 

 after sterilization it is injected into a healthy guinea pig, it has 

 practically no effect. If into a second guinea pig tubercle bacilli 

 are injected the usual lesions appear in from four to six weeks. If, 

 however, into a third guinea pig the sterile exudate and a com- 

 paratively small quantity of tubercle bacilli are injected death 

 follows within twenty-four hours, indicating that the exudate 

 had a paralyzing effect upon the defensive forces of the animal 

 cells, thus greatly increasing the virulence of the bacilli. That the 

 effect is not produced by endotoxin in the sterilized exudate is 

 proved by the fact that the exudate alone produced no reaction. 

 Similar results are obtained with other organisms such as typhoid 

 and dysentery bacilli, cholera spirilla, etc. It has been assumed 

 therefore that the exudate contains a substance which enables the 

 bacilli to become more aggressive. Consequently this hypotheti- 

 cal substance has received the name aggressin. It is believed that 

 it has a paralyzing effect upon the polynuclear leukocytes, which, 

 as we shall see later, constitute one of the body's strongest defenses. 

 In general the production of aggressins is most abundant when the 

 body resistance is greatest. It is thought by certain authorities 

 that aggressins are secreted by bacteria as a means of protection 

 against the opposing forces of the animal cells, just as the body 

 cells produce antitoxin to neutralize bacterial toxin. According to 

 this theory toxins may be considered as the offensive agents of 

 bacteria and aggressins as their defensive weapons. 



