IMMUNITY AND ANAPHYLAXIS 195 



began with chronic staphylococcal infections, and in such 

 cases good results were obtained. The method has been 

 applied to infections by tubercle bacilli, streptococci, 

 gonococci, pneumococci, and other bacteria. If possible, 

 a culture is made from the actual bacteria causing the 

 infection. From the culture so made, an emulsion in 

 sterile salt solution is obtained, and the emulsion sterilized 

 at the lowest possible temperature (usually 65 C. for one 

 hour), and an agar inoculation made from the presumably 

 sterile emulsion, and incubated for twenty-four hours 

 to see if really sterile. The bacterial content of the 

 emulsion must be estimated, so as to be able to know how 

 many are being injected, and to inject a definite quantity. 

 This is done by mixing equal quantities of the emulsion 

 (whole or diluted) and fresh blood, and making films, and 

 staining. The number of bacteria to red cells is noted 

 over a field made by drawing a circle with a blue pencil 

 on the lens of the eye-piece of the microscope. The 

 number of red cells in the blood being known (say 5 million 

 per c.mm.), and the relative proportion of bacteria in 

 undiluted emulsion to the red cells being, say, 700 to 400, 

 then as 400 : 700 : : 5,000,000 : x = 8,750,000 bacteria per 

 c.mm. If the emulsion had been diluted, then the result 

 would have to be multiplied by the number of the dilutions. 

 It is preferred that the content be estimated before 

 sterilization, as some of the bacteria may undergo 

 disintegration during that process. Where the blood 

 serum has an agglutinating effect, the red cells are separated 

 and mixed with salt solution. It is better to render 

 motile bacilli still by having a little formol in the saline 

 solution. From the stock emulsion thus standardized 

 and sterilized, appropriate doses are made by dilution 

 with 0-5 per cent phenol or lysol solution, and put in glass 

 bulbs, with capillary ends which are sealed. The ordinary 

 dosage is to begin with 100 million and to repeat, if necessary 

 using a larger dose, after estimating the opsonic index, and 

 only if this is rising. Numerous observations after the 

 injection of such vaccines have shown that the opsonic 

 indexi^falls for some time thereafter (" Negative Phase ") 

 and then begins to rise, and usually ascends to a higher 

 level than before. Another injection during the negative 



