CHAPTER VI. 



THE NATURE OF IJIMDNITY-GIVING SUBSTANCES. 



Ogata and Jasuhara find that anthrax bacilli grown 

 in the blood-serum of animals naturally immune to the 

 disease will not on subsequent inoculation induce the dis- 

 ease in animals naturally susceptible. Thus, anthrax 

 germs grown in frog-blood make mice sick, but do not 

 prove fatal to them, and those grown on the blood-serum 

 of white rats or dogs have a similar eifeet upon rabbits ; 

 but germs grown in the blood of animals not immune kill 

 both mice and rabbits. They also find that the injection 

 of one drop of frog blood-serum or one-half drop of serum 

 from a dog into a mouse, any time within seventy-two 

 hours before to five hours after inoculation with anthrax, 

 protects this animal from the disease. A guinea-pig weigh- 

 ing 400 grammes was given twenty drops of frog's blood 

 diluted with the 0.6 per cent, salt solution and immediately 

 thereafter inoculated with virulent anthrax ; the animal 

 became slightly sick, but soon recovered. The same was 

 true of a rabbit weighing 1500 grammes which was treated 

 with 8 c.c. of defibrinated dog's blood. The experimenters 

 conclude that one-fourth of a drop of the serum of the dog 

 diluted to three times its volume with the salt solution is 

 the smallest amount which will give immunity against 

 anthrax to a mouse of 10 grammes. 



KiTASATO and Behring have secured immunity in 

 some animals against tetanus and diphtheria by the follow- 

 ing methods : 



(1) By the method of Frankel (for diphtheria), which 

 has been given. (See page 128.) 



(2) By the addition of iodine trichloride to cultures four 

 weeks old, in the proportion of 1 : 500 ; allow to stand for 

 sixteen hours ; inject 2 c.c. into the abdominal cavity of a 



