I0O PATHOGENIC BACTERIA, 



power, it being the rule that the bloods of immune ani- 

 mals act most destructively upon those bacteria against 

 which the animal has the greatest resisting power. Thus, 

 the rat which is immune to anthrax, has blood that is 

 very destructive in its action upon the anthrax bacillus. 

 However, the rule is one to which there are many puz- 

 zling exceptions, for the dog is also quite resistant to an- 

 thrax, though its blood is harmless to the bacilli, and the 

 rabbit is susceptible to the disease although its blood is 

 destructive to them. 



The power of the blood to destroy bacteria is not unlim- 

 ited, for Nissen l found that when a few cholera spirilla 

 are added to freshly-drawn rabbits' blood they are killed 

 in about thirty minutes, but if the number exceeds about 

 one million per cubic centimeter they increase in number. 



Behring 2 , endeavored to study the germicidal value of 

 blood serums so as to measure their activity as compared 

 with corrosive sublimate and carbolic acid, and found that 

 u one part of fresh serum of the white rat added to eleven 

 to fifteen parts of the serum of sheep (which is not anti- 

 septic to anthrax) would prevent the growth of the bacilli 

 in the latter; 3.5 c.c. of rats' serum mixed with an 

 equal part of sheeps' serum would completely destroy, in 

 twenty-four hours, the bacilli coming from the blood of a 

 guinea-pig affected with anthrax. To obtain the same 

 preventing and sterilizing action in sheeps' serum with 

 corrosive sublimate and carbolic acid, it was necessary 

 to use the first in the proportion of 1 : 1000, and the 

 second of 2 : 100." 



In cases in which the activity of the serum does not 

 kill the bacteria it frequently attenuates them ; and it 

 may be that the immunity of animals whose serums 

 are not germicidal depends upon attenuating substances 

 which, robbing the organisms of their pathogenesis, 

 enable the animal to dispose of them. 



The destructive and inhibiting powers of the serum 



1 Zeitschrift fur Hygiene, 1889, vi., p. 487. 



* Die Bekampfung des Infektionskrankheiten, Leipzig, 1894, p. 493. 



