In summary, as a result of inquiry into the basic factors governing these 5 technics, the iodine-dilution technic has been found to be slightly more efficient in the actual quantitative recovery of diagnosable Endamoeba coli and E. histolytica cysts from a given amount of fecal material than is the hematoxylin-film technic or centrifugal floatation. It is considerably more efficient than centrifugation and superior to sedimentation. However, when the factors of concentration are considered, the apparent enrichment by centrifugation may be 4- or 5-fold that of the iodinedilution technic, while centrifugal-floatation, using zinc sulphate solution (sp. g. 1.180) as the diluent, provides a concentration which may be as high as 1000-fold.
We are now testing the centrifugal-floatation technic, with zinc sulphate as the levitating medium, for comparison with the iodine-dilution technic in routine fecal diagnosis. As soon as an adequate series of specimens has been examined and the results have been analyzed, we expect to be in a position to recommend a simplified, practical method for clinical laboratory diagnosis of parasites in feces.
This investigation is being conducted by the Amebiasis Unit of the National Institute of Health at Tulane University, organized and directed by Ernest Carroll Faust. The separate phases of the problem have been studied principally by the following persons: (1) basic homogeneous suspension of feces, Joseph S. D'Antoni and Vada Odom; (2) iodine dilution technic and counts, Joseph S. D'Antoni, Vada Odom and Willi Sawitz; (3) hematoxylin-film technic and counts, Max J. Miller and Charles Peres; (4) sedimentation technic and counts, J. Henry Walker; (5) centrifugation technic and counts, Willi Sawitz and Luis F. Thomen, and (6) centrifugal-floatation technic and counts, John Tobie.