834 EXPERIMENTAL INFECTION AND IMMUNITY 



EXERCISE 14. OPSONIC INDEX 

 EXPERIMENT 40. DETERMINING THE OPSONIC INDEX 



1. Secure a small quantity of blood from a guinea-pig or rabbit which has been 

 immunized with Staphylococcus pyogenes aureus. Also two specimens from normal 

 animals to serve as control serums. Remove the serums, being careful to keep them 

 marked and separate. The two normal serums may be mixed in a watch-glass or 

 small test-tube (pooled). 



2. Prepare a leukocyte mixture, using normal guinea-pig or rabbit blood according 

 to the immune animal used. 



3. Prepare a bacterial emulsion of an eighteen-hour culture of Staphylococcus 

 pyogenes aureus. 



4. Proceed to determine the phagocytic and opsonic index as per technic given in 

 the text (page 195). 



(a) What constitutes a satisfactory bacterial emulsion? 



(b) What constitutes a satisfactory leukocytic suspension? Name 

 several methods of obtaining leukocytes for this technic. 



(c) What constitutes a satisfactory phagocytic film? 



(d) Should the serum be fresh? 



(e) How do you determine the phagocytic index? 



(f) How do you determine the opsonic index? 



(g) What is the relation between the opsonic and phagocytic indices? 

 (h) Give the practical value of the opsonic index in disease. 



(i) Give the practical value of the opsonic index as a measure of 

 immunity. 



Note. If any of the students have received typhoid vaccine, the 

 opsonic index with his serum may be determined. 



EXPERIMENT 41. QUANTITATIVE ESTIMATION OF BACTERIOTROPINS 



1. Secure a culture of pneumococcus. 



2. Secure a few cubic centimeters of antipneumococcus serum, especially a serum 

 corresponding to the culture. 



3. Prepare a leukocytic emulsion. 



4. Conduct the test after the technic given in the text (page 200). 



(a) Give the value of a bacteriotropic estimation of a serum. 



(b) What relation do bacteriotropins bear to immunity? 



(c) In what class of diseases are bacteriotropins of most value? 



EXERCISE J5. BACTERIAL VACCINES 

 EXPERIMENT 42. PREPARATION OF TYPHOID VACCINE 



1. Prepare two to six agar slant cultures of Bacillus typhosus and grow for forty- 

 eight hours at 37 C. 



2. Remove cultures, prepare a suspension count by the method of Wright, 

 sterilize, dilute, and prepare vaccine for administration as given in the text. 



