APPENDIX. 



Aggressins. 



A FURTHER contribution has recently been made to the problems of 

 virulence and immunity in the form of the " aggressin theory " of Bail. 1 

 Apparently it grew out of an attempt to explain the so-called " phe- 

 nomenon of Koch " an observation made years ago by Koch to the 

 effect that tuberculous animals when inoculated intraperitoneally with 

 a fresh culture of tubercle bacilli succumb quickly to an acute attack 

 of the disease, the resulting exudate containing almost exclusively 

 lymphocytes. Bail found that if tubercle bacilli, together with steril- 

 ized tuberculous exudate, were injected into healthy guinea-pigs, 

 the animal died very suddenly i. e., in twenty-four hours or there- 

 abouts. The exudate alone had no appreciable effect on the animal, 

 while inoculation with tubercle bacilli alone produced death in a 

 number of weeks. He therefore concludes that there is something in 

 the exudate that allows the bacilli to become more aggressive, and 

 hence has called this hypothetical substance " aggressin/' He thinks 

 it is an endotoxin liberated from the bacteria as a result of bacteriolysis 

 and that it acts by paralyzing the polynuclear leukocyte, thereby pre- 

 venting phagocytosis. Heating the exudate to 60 C. increases its 

 aggressive properties rather than diminishes them and small doses act 

 relatively more strongly than larger ones. These facts he explains by 

 assuming the presence of two properties, one that prevents rapid death 

 is thermolabile and acts feebly in small doses, and one that favors 

 rapid death and is thermostabile. He assumes that in a tuberculous 

 animal the tissues are saturated with the aggressin and when fluid col- 

 lects in the body cavities, as it does on injection of tubercle bacilli, it 

 contains large quantities of aggressin, which prevents migration of the 

 polynuclear le'.ikncytivs but not of the lymphocytes, and hence allows the 

 bacilli to develop freely, producing acute symptoms. In the peritoneal 

 cavity of the normal animal injected with tubercle bacilli, on the other 

 hand, are large numbers of polynuclear leukocytes which engulf the 

 bacilli, thus inhibiting their rapid development, there being here no 

 aggressin to prevent phagocytosis. 



This theory has been applied to a number of infections, includ- 

 ing typhoid, cholera, dysentery, chicken cholera, pneumonia, and 

 staphylococcus infections. In all similar results have been obtained as 



1 Wiener klin. Woch., 1905, No. 9. Ibid., 1905, Nos. 14, 16, 17. Berliner kliri. Woch., 1905, 

 N... 15. Zeit. f. Hyg., 1905, vol. i. No. 3. Arch. f. Hyg., vol. Hi. pp. 272 and 411. 



