CONTROL OF INJECTION OF VACCINE. 09 



her of bacteria per cubic centimeter of the suspension is deter- 

 mined by drawing into a capillary pipette one volume of the 

 bacterial suspension, and one or more volumes of fresh blood 

 from a puncture in the finger. These volumes are then mixed 

 well and a drop of the mixture placed on a clean slide. With a 

 spreader which is placed in front of the drop, a smear is made. 

 This is then allowed to dry, is fixed and stained with a suitable 

 stain, usually Loeffler's methylene blue. The slide is then counted 

 by determining the number of red blood cells and bacteria in 

 from ten to twenty-five fields of the high power of the microscope. 

 Normal human blood contains five million red blood cells per 

 cubic millimeter. After having established the ratio of red blood 

 cells to the bacteria in the suspension, it is easy to determine the 

 number of bacteria per cubic millimeter or cubic centimeter. 

 The tube containing the bacterial suspension is now sealed and 

 heated in a water bath, to 60 or 65 C. for one hour. After kill- 

 ing the bacteria in the suspension, a dilution, suitable for injection, 

 is made in a bottle containing 50 c. c. of sterile salt solution. 

 The bottle is closed with a rubber cap and sufficient carbolic acid 

 or lysol is added to make an ultimate dilution of O.o per cent. 

 After this the vaccine is tested for sterility on suitable culture 

 media. To obtain vaccine from the bottle a drop of pure lysol 

 is placed on the rubber cap. This is done to sterilize the outer 

 surface of the rubber cap. Then the sterile hypodermic needle 

 is inserted through the cap, the bottle turned up and the piston 

 of the syringe is withdrawn until the desired amount of vaccine 

 has been taken into the barrel of the syringe. 



CONTROL OF INJECTION. 



While Wright and his pupils have claimed to regulate the 

 dosage and inter-spacing of injections entirely by the opsonic 

 index, others have found the opsonic index too unreliable to serve 

 as a guide in the administration of bacterial vaccines. Wright 

 and his pupils have not always based their decisions on dosage 

 and time for injection, on determinations of the opsonic index. 

 It frequently happens that at the time of the first injection of 

 vaccine their patients have an opsonic index well above normal. 

 In most cases the treatment is based on determinations made by 

 serum drawn twenty-four hours earlier. The time for the second 



