176 LABORATORY COURSE IN SERUM STUDY 



III 



Set up a third series of three tubes containing immune serum which 

 has been heated at 56 for half an hour. After heating, dilutions of 

 1-5, 1-10 and 1-20 should be prepared, and 0.25 of each dilution added 

 to one of the tubes. 



To each of these tubes now add 0.1 c.c. of bacterial suspension 

 and 0.2 c.c. of washed leucocytes. Incubate for one half hour and pre- 

 pare smears from the sediment of each tube. Stain the smears with 

 Jenner's stain and count the number of bacteria contained in 50 leuco- 

 cytes in each smear, calculating the average number per leucocyte. 

 Any slide which shows a definite increase above the salt solution should 

 be regarded as showing positive opsonic power in the corresponding 

 dilution of serum. 



Materials: same as three preceding lessons. 



15 -inch tst tubes. 5 J-inch test tubes. 



LESSON XXXI 

 PREPARATION OF BACTERIAL VACCINE 



THE preparation of bacterial vaccines consists in four steps : 



I. PREPARATION OF THE EMULSION 



Each student is given two agar slants of Staphylococcus aureus of 

 24-hour growth. To each tube add about 2 c.c. of sterile salt solution 

 with a sterile pipette. Remove the bacteria from the surface of the agar 

 by scraping gently with a sterile platinum loop, being careful not to cut 

 into the surface of the agar. When an even suspension is obtained this is 

 transferred to a small sterile bottle or test tube containing glass beads 

 and thoroughly shaken to break up clumps of the organisms. 



II. STANDARDIZATION 



The second step in the preparation of vaccine is to determine the 

 number of organisms contained per c.c. 



(a) Hcemocytometer Method 



A staining solution is prepared by adding to 20 c.c. of 1 per cent 

 phenol 1 c.c. of a saturated alcoholic solution of thionin. A small 



