MECHANISM IN INFECTIONS WITH TRUE PARASITES 81 



infinitesimally small quantities are sufficient to produce death; 

 whose manner of action, moreover, is such that the focal infection 

 may long have ceased to exist, while the toxin is being conveyed to 

 and brought into contact with cells, damage to which leads to the 

 death of the patient. 



In an infection of this sort the local superiority of those defensive 

 forces of the host with which we have thus far become acquainted, 

 over the purely vegetative forces of the invader, is evidently totally 

 insufficient to preserve the life of the infected individual, unless, 

 indeed, the disproportion between the number of the infecting germs, 

 and the protective forces at the point of attack should be so greatly 

 in favor of the latter, that no multiplication of the bacteria occurs at 

 all, and then only provided that the number of invading organisms 

 is so small that the amount of toxin which they could secrete before 

 being killed would be insufficient to cause death. Theoretically this 

 possibility could certainly exist. Whether it enters into considera- 

 tion practically is beyond our knowledge. 



This type of infection illustrates two points very well, viz., that the 

 destruction of the invading bacteria at the point of entry does not 

 necessarily prevent the development of symptoms of systemic dis- 

 ease and even of death, and that the protective forces with which 

 we have thus far become acquainted are inadequate to counteract 

 the deleterious influence of toxins of this order. 



Offensive-defensive Mechanism in Infections with True Parasites. 

 In infections with organisms like the anthrax bacillus the situation 

 is altogether different. The picture which is here seen has been 

 analyzed with great care by Bail, whose account I am here following 

 in some detail. 



If a guinea-pig or, still better, a rabbit is injected intraperitoneally 

 with a moderate amount of a broth culture (J to 1 c.c.) of the anthrax 

 bacillus, and small specimens of the peritoneal fluid are removed from 

 time to time, it will be observed, after a short while, that the bacilli 

 show external marks of degeneration, and are being extensively 

 taken up by the leukocytes, which have appeared in large numbers, 

 and undergo intracellular degeneration. 



Evidently some of those defensive forces with which we have just 



become familiar (opsonins, alexins) are here at work, and unless 



the number of organisms injected has been too large, these normal 



protective forces are apparently sufficient to successfully combat the 



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