124 INFECTION 



develop substances in their serum that are bactericidal, bacteriotropic, 

 and agglutinative to the bacteria from which the poisons were derived, 

 but the serum itself is not antitoxic for the endotoxins. Therapeutic 

 serums for use against infections caused by the endotoxin class of 

 bacteria are largely bacteriolytic and bacteriotropic in action. The 

 endotoxins of some bacteria, and particularly those of streptococci, 

 seem to repel the leukocytes, or exert a negative chemotactic influence, 

 which may effectually retard or entirely prevent phagocytosis; in this 

 respect they resemble the aggressins of Bail. Immune serums owe a 

 portion, at least, of their therapeutic value to the power they possess of 

 overcoming this influence and facilitating phagocytosis. These serums, 

 however, have not proved of as much value as have the diphtheria and 

 tetanus antitoxins in the treatment of the respective infections men- 

 tioned, and have proved a check to the progress of serum therapy. It 

 is probable that the endotoxins are more specific for the various strains 

 of the same species than are the true toxins, as indicated by the results 

 of Cole in the treatment of pneumonia with an anti-pneumococcus 

 serum corresponding to the type of microorganism responsible for the 

 individual infection, as determined by a rapid method of diagnosis 

 previous to the administration of serum. 



AGGRESSINS 



In an attempt to explain certain observations of Koch to the effect 

 that when a tuberculous animal is injected intraperitoneally with a fresh 

 culture of tubercle bacilli it succumbs quickly to an acute atta^ of the 

 disease, the resulting exudate being composed almost exclusively of 

 lymphocytes, Bail 1 has advanced the hypothesis that bacteria may 

 secrete aggressins, or substances that aim to protect the microorganism 

 by either neutralizing the action of opsonins or directly repelling the 

 body-cells and preventing phagocytosis. Bail found that if he removed a 

 tuberculous exudate, sterilized it, and injected it into healthy animals, 

 it had practically no effect. If tubercle bacilli were injected alone, 

 lesions would develop in the usual number of weeks; but if sterile 

 exudate and tubercle bacilli were injected together, death would follow 

 in about twenty-four hours, indicating that the exudate contained a 

 substance that acutely paralyzed the defensive forces of the animal, and 

 thus greatly increased the virulence of the bacilli. That this effect was 

 not the summation of endotoxins in the exudate plus living microorgan- 



1 Wien. klin. Woch., 1905, 8, 14, 16, and 17; Berl. klin. Woch., 1905, 15; Zeit. 

 f. Hyg., 1905, i,13; Arch. f. Hyg., 1905, 52, 272, and 411. 



