Page:Tropical Diseases.djvu/574

530 Giemsa. The films are made on cover-glasses, fixed in osmicacid vapour, rinsed in distilled water, and stained with dilute Giemsa (1:20 dilution). This method is not so good as the foregoing for demonstrating the nuclear structure. Isolation of B. dysenteric from the stools.— The stool is collected under as aseptic conditions as is possible. A flake of mucus is taken up with a sterilized platinum loop and diluted with sterile normal saline or broth. Some observers prefer to incubate in McConkey's bile-broth, which inhibits the growth of all but bacilli of the coli group. Large plates (6-in. Petri dishes) of Conradi-Drygalski medium* (crystal-violet-litmus-lactose-nutrose agar), or of lactose-neutral-red agar,† are then spread in various dilutions and incubated. On Conradi-Drygalski the colonies of the dysentery bacillus are recognizable in twenty-four hours by their transparent blue colour, and on neutral-red-agar by their transparency in contradistinction to the red colonies of B. coli. Such colonies often smell strongly of spermin. The bacilli are further recognized by their morphology, their Gram-negative character, their sugar reactions, agglutination tests with the patient's serum and a polyvalent serum, and further b) T their toxic action on guineapigs when injected intraperitoneally.

In African and West Indian cases the possibility of bilharzia disease must be borne in mind, and a microscopical examination made of the urinary sediments and of the faeces. So, too, in cases from the Far East, Schistosomum japonicum and other intestinal and hepatic parasites must not be forgotten. In children, especially, intussusception may occur independently, or as a complication of dysentery; the possibility of this must not be overlooked.

Chronic dysentery is often diagnosed chronic diarrhœa or even sprue. This error will be avoided by careful inquiry into the early history of the case, the detection of mucus, of amoebae, of leucocytes or of red blood-corpuscles in the stools, and the occurrence of tenesmiis. Careful inquiry for any history there may be of occasional exacerbations in which straining, d blood and mucus in the stools, are more or less