In contrast to these findings on fresh stool, Goldman and Brooke (1953) claim that trophozoites are to be found in faeces preserved with polyvinyl alcohol (P.V.A.), though it is not clear from their report whether E. histolytica is included in this category; and Brooke, Donaldson, and Brown (1954) recommend P.V.A. fixation for trophozoites in conjunction with form'olether concentration for cysts and ova. We have not so far had much success with P.V.A. fixation, partly perhaps because stools sent to this laboratory are all relatively fresh (they are examined within two to three hours, unlike Goldman and Brooke's material) and partly because the incidence, of trophozoites in our present material is low.There appears to be no simple solution to the problem of finding E. histolvtica trophozoites in chronic infections. Occasionally ulcers (with numerous trophozoites) are seen at sigmoidoscopy, though the parasites are not to be found in repeated stool examinations.
SummaryThe value of the formol-ether method of concentrating faeces is emphasized as a diagnostic routine for intestinal parasites. A simplified technique is described, which takes only five minutes to perform.All cysts and ova are concentrated without distortion. Faecal cysts were found nearly twice and ova three times as often as by direct searching.Although the concentration procedure destroys freeform amoebae and cellular exudate, additional direct examinations of formed stools free of blood and mucus produced no new findings in this series of cases. 24, 1955) The antigen commonly used in the complementfixation test for toxoplasmosis is made from infected egg membranes (Sabin, 1949), and it is difficult to prepare it free of blood pigments. The antigen is stored at -200 C.It was seen that on thawing the antigen the blood pigments were concentrated at the bottom of the container, and it was hoped that this separation might be used in making an effective antigen relatively free from blood pigments. This would be possible only if the antigen were concentrated at a different level from blood pigments.
MethodTo determine whether or not this was possible, 31 ml.of antigen was prepared and stored at -200 C. in two parts, one of only 1 ml. and the other as a column of 30 ml. The smaller part was left as a sample of the original preparation. After 18 hours at -200 C. the sample and column were thawed slowly at room temperature. The column was carefully divided into upper and lower halves, each of which was then mixed before taking a 1 ml. sample of each. This left two portions of 14 ml. each which were again frozen in a column for 18 hours at -20°C. The thawing, dividing, sampling, and refreezing process was repeated four times in all. Finally, there were 31 samples, all of which had been frozen and thawed four times.The samples were tested for haemoglobin colour, antigenic potency, specific gravity, and sodium chloride concentration as follows:Index of Colour.-The samples were viewed against a white background and arranged in order from 1 to 31, varying fr...
