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XXIX] diagnosis, in severe cases of amoebic origin (such as those described by Kuenen and others, and in which gangrenous sloughs are common in the stools) the amœba cannot as a rule be demonstrated during life, though it may be found in sections of the gut post mortem. In such cases it seems probable that the amœba has been removed from the superficial layers of the bowel by a secondary bacterial infection. It is necessary to bear this in mind in view of the specific treatment appropriate to these apparently desperate cases (see p. 538). And for the same reason it must not be overlooked that cases of mixed infection with B. dysenterice and Entamceba histolytica do occur; such cases have been reported by Rogers.

In order to obtain permanent preparations it is necessary to fix the amœbæ while still alive; desiccation distorts them to such an extent as to obliterate all their liner structural characters. For this purpose Schaudinn and Wasieliewski have invented a special technique which gives perfect pictures of the nucleus, disposition 'of protoplasm, vacuoles, etc. The following is a summary of their rather complicated methods:—

1. Schaudinn's method.— Can be used either for demon- strating amœbæ in films or an abbreviated form for showing the organisms in sections of tissue. A thin film of the mucus is made on a cover-glass and dropped while still wet, face downwards, into a Petri dish containing a fixing mixture, which should be heated to steaming-point (50° C.).
 * (1) Fixing mixture. Absolute alcohol, ½; corrosive sublimate,⅔; and ½ per cent, glacial acetic; fifteen minutes.
 * (2) Rinse in weak spirit.
 * (3) Alcohol 70 per cent.; ten minutes.
 * (4) Alcohol 70 per cent, and iodine (to dissolve corrosive sublimate); half an hour.
 * (5) Alcohol 90 per cent.; twenty minutes to one hour.
 * (6) Through alcohols of decreasing strength to tap- water.
 * (7) Place film upwards in 4-per-cent. iron-alum overnight.
 * (8) Rinse in distilled water and place in Heidenhain's iron-hæmatoxylin solution six to twenty-four hours.
 * (9) Differentiate in 1 -per- cent, iron-alum solution under microscope till nuclei of amœbæ are clear.
 * (10) Pass through increasing strength of alcohols up to absolute, then two changes of xylol, and mount in Canada balsam.

N.B. The films must not at any time be allowed to dry. 2. Wasieliew ski's method.— Wasieliewski has obtained (1913) very beautiful specimens of amœbæ stained by