114 
TENTH REPORT. 
vaccine) or it may be made from corresponding bacteria obtained from 
similar cases (stock vaccines). 
In gonorrhea, stock vaccines must be largely used, owing to the difficulty 
encountered in many cases in obtaining autogenous cultures. The same 
is true in tuberculosis, with the added factor that the germs must be pre- 
pared for absorption by rather elaborate processes; the best known of the 
resulting products being Tuberculin, T. R. and Tuberculin B. E. 
In the other infections, autogenous vaccines can be readily made by those 
Fig. 1. — Emulsifying bacteria. 
having laboratory facilities and training, or stock vaccines may be used. 
Whether autogenous vaccines are markedly superior to stock vaccines has 
not yet been determined. 
The various steps in determining the opsonic index and making bacterial 
vaccines will now be taken up in detail. 
Preparing the Emulsion of Bacteria . — The culture 
of the germ in question growing on inclined agar 
is removed and emulsified, the method of emulsi- 
fying depending upon the character of the germs, 
and upon the age of the culture. In a young cult- 
ure (12 to 24 hours) it is usually sufficient to wash 
off the culture with 0.85 per cent salt solution and 
draw it up and down repeatedly in a pipette (see 
Fig. 1). In the case of bacillus tuberculosis the 
emulsion may be made from fresh culture, or from 
dry, dead tubercle germs. These need considerable 
grinding to properly emulsify them. After emul- 
sifying and diluting, the suspension is centrifugal- 
ized to remove the clumps of bacteria (see Fig. 2) 
and then tested for density by determining its 
■phagocytic index when opsonized with normal se- 
rum. The proper consistency is one that will give 
a count of about two bacteria per leucocyte for 
tubercle, and a count of from three to five for other germs. 
Fig. 2.— Tube of bacterial 
suspension ready to centrifu- 
galize, with a companion tube 
equally filled with water to 
balance the centrifuge. 
The best 
