The statement is frequently made by. physicians that the technic of the Wright-Douglas vaccine treatment and the determination of the opsonic index is so complicated and burdensome that without a well-equipped laboratory the work can never become practicable.
While experimenting on some phases of opsonic work it occurred to me that some method should be devised to make the determination of the opsonic index available to the physician with limited laboratory facilities. I have, therefore, devised and investigated the following method, which seems to be very efficient:
A culture of the bacterium to be opsonized is grown on agar-agar, blood serum or some other solid culture media and after incubation at 37 degrees C. for eighteen to twenty-four hours is washed off with a small amount of sterile 0.85 per cent, sodium chlorid and 0.8 per cent, sodium citrate solution.
In place of the regular capillary opsonic pipette the leucocyte