In the American Journal of Tropical Medicine for July, 1927, Colonel Charles F. Craig, M. C., U. S. A., described a complement-fixation test for detecting the presence of infection with Endamoeba histolytica. Ever since that time efforts have been made to perfect a pure E. histolytica antigen, free from bacterial content. The antigen prepared by the following method is practically bacteria-free and seems to be of greater value as a diagnostic aid in amebiasis than those formerly used.
PREPARATION OF ANTIGEN
1.Collection of cysts. Take twelve to twenty cultures (prepared as recommended in the preceding paper), containing on an average 1,800,000 cysts per culture, and allow them to stand in a vertical position in an ice-box for twenty-four hours. All of the cysts will now be in the bottom of the tubes. Carefully draw off and discard all but 1 cc. of the supernatant fluid by means of a suction pump, large dropper or pipette.