BACTERIAL DISEASES OF MAN AND ANIMALS 93 



Koch's achievement was due to his success in cultivating the 

 anthrax bacillus outside the body in a pure culture, apart from 

 any fluids or tissues of the diseased animal, and in being able to 

 produce the disease by introducing these germs into the bodies 

 of healthy animals. 



The spores, likewise discovered by Koch, have been the subject 

 of much biological study. Spores are only produced in the 

 presence of free oxygen and at temperatures between 14 and 

 40 C. They are extremely resistant to drying, it having been 

 shown experimentally that they may retain their vitality for 

 eighteen years, and then produce the disease when inoculated 

 into susceptible animals. The spores are not so resistant to heat 

 as those of some saprophytic forms, but they are quite resistant 

 to disinfectants. 



Vaccination with cultures attenuated by heat is now largely 

 used to protect animals against anthrax and is quite successful. 

 Immune sera are used on human subjects. 



1. Observe the instructor inoculate a guinea pig with a pure 

 culture of B. anthracis. At the next laboratory period make a 

 post-mortem examination of the animal. Note the condition of 

 the various internal organs. 



2. Inoculate tubes of bouillon from the spleen and tubes of 

 agar from the heart blood. 



3. Make smear preparations from the spleen. Hold the tissue 

 with sterile forceps and rub it over a clean slide. Dry, fix, and 

 stain with Gram's stain. 



4. Place a small drop of blood on a cover glass, add a drop 

 of sterile physiological salt solution, mix, and dry. Stain with 

 methylene blue. 



5. Examine and draw a field from each slide. 



6. From your observations, how do you explain the death of 

 the animal infected with anthrax ? 



7. Make stained preparations from the tubes made in 2. 



8. When spores appear, make a spore stain according to direc- 

 tions in Exercise 61. 



9. Make and describe cultures upon gelatin stab and gelatin 

 plate. 



