Technical Methods on Formol-ether Concentration
The simplified version of Ritchie’s formol-ether technique for the concentration of faecal cysts, ova, and larvae (Ridley and Hawgood, 1956), which is no less effective than the original, has been quite widely adopted as a useful routine diagnostic procedure. With further experience, however, three objections have become apparent, which apply also to some other concentration methods: (1) The degree of concentration of Taenia and Ascaris (especially infertile Ascaris) ova is unsatisfactory in some cases; and the concentration of Schistosoma ova is less than optimum. (2) It is difficult to make the concentrated deposit adhere to a microscope slide for fixation and staining. (3) The concentration of faecal specimens, fixed in bulk and stored for a period of days or weeks, is unsatisfactory. The object of the present paper is to describe further simple modifications which overcome the first two of these objections.