60 BACTERIOLOGY FOR NURSES 



alexines, and the degree of immunity was dependent 

 upon the amount of alexines contained in the blood; 

 but it has been found that in some cases there is no 

 relation between the resistance of the animal and the 

 bactericidal power of its blood-serum. The human 

 blood-serum is strongly bactericidal for the bacillus 

 of typhoid fever, but that fact does not always pre- 

 vent the multiplication of the organism in the blood 

 during an attack of the disease. The chief difference 

 between an antitoxic serum and a serum which is 

 bactericidal is, that an antitoxin acts only upon a 

 formed poison, while a bactericidal serum may be 

 protective, preventing an infection. The antitoxin 

 of diphtheria affords the best example of an antitoxic 

 serum; it not only neutralizes the diphtheria toxin, 

 but is also curative. 



Certain bactericidal sera which are bacteriolytic 

 (dissolving) in their action have been used only in a 

 limited degree in the diseases of man, as they can only 

 be artificially cultivated in the lower animals and 

 have not always proved satisfactory, because of the 

 differences in species, it is supposed. The blood- 

 serum from animals inoculated with typhoid bacilli 

 has been found entirely ineffective when used for 

 treating the disease in man; and on the other hand, 

 the use of the bacterial cells by vaccination as a 



