QUESTIONS AND ANSWERS 163 



What are agglutinins? 



Substances in the blood-serum which have the property of 

 agglutinating or clumping bacteria. These substances are present 

 in normal serum but are very abundant in the serum of animals 

 immunized to, or suffering from certain diseases. This property is 

 utilized as a diagnostic agent. 



If unexpectedly called upon to do so, how could one properly collect 

 tissues in the country for bacteriologic examination? 

 Procure a fruit-jar with a tight-fitting cover. Boil same for 

 thirty minutes. Open the animal and, with a sterilized knife, cut out 

 and carefully place in the jar, specimens desired to be examined; 

 avoid contaminating with any other objects; seal quickly, using 

 paraffin over the top. 



What is the opsonic index? How is it determined? 



The opsonic index is the measure of the power of the blood-serum 

 of an infected individual to prepare bacteria for phagocytosis, com- 

 pared with the serum of a healthy individual. 



It is determined by mixing a known quantity of bacterial sus- 

 pension with equal quantities of blood serum and an emulsion of 

 healthy leucocytes. After incubating the mixture long enough to 

 permit the opsonins to act on the bacteria and phagocytosis to take 

 place, slides are prepared and stained, and the average number of 

 bacteria in a leucocyte determined. (One hundred or more leuco- 

 cytes should be examined to obtain average.) If 100 leucocj^tes 

 take up 400 bacteria when treated with healthy serum, and 100 

 leucocytes take up only 300 of the same bacteria when treated with 

 the patient's serum, that patient's opsonic index is (400:300 = 

 1:X) X=0.75. 



What is the cause of the following diseases: (a) surra, (b) Johne's 

 disease, (c) hog cholera, (d) actinomycosis. 

 (a) Trypanosoma Evansi; (b) bacillus paratuberculosis ; (c) 

 filterable virus, associated with B. cholera suis; (d) ray fungus. 



What diseases are caused by the bacillus necrophorus? 



The necrosis bacillus causes foot rot in sheep and cattle ; necro- 

 bacillosis of the liver, lips, mouth, vagina, sheath, penis ; and various 

 gangrenous processes. 



What is (a) an antitoxin, (b) a toxin, (c) a bactericidal serum, (d) 

 bacteriolytic serum, (e) exotoxin, (f) endotoxin? 



(a) A substance in the senun which binds and neutralizes toxin; 



