THK THYPANOSOMA BRUCIl. 458 



are methylen blue and erythrosin; the methylen blue used 

 must be tlie methylen blue med. pur. (Hoclist). A 1 percent, 

 solution in distilled water is made, and to it '5 per cent, 

 potassium carbonate is added and dissolved ; the mixture is 

 then incubated at 37° for forty -eight hours ; when cold it is 

 filtered, and is then ready for use. Instead of using eosin 

 (under Avhich name many substances of different shades and 

 of different composition are sold) for the second stain, we 

 have found it far more certain and effective to use erythrosin 

 (the tetraiodide of fluorescein), which, as found in commerce, 

 is of more definite and constant composition and colour than 

 eosin; a '001 per cent, solution is made, to which '25 per 

 cent, formalin can be added in order to prevent the growth 

 of moulds. Of these two solutions we have found the 

 following to be the best mixture for demonstrating the 

 different structures in the Trypanosoma : 20 c.c. of distilled 

 water are put into each of two beakers, to one of which is 

 added twenty drops of the erythrosin solution, and to the 

 other six to eight drops of the methylen blue solution. 

 These solutions are then quickly mixed, and are immediately 

 poured into a fiat dish^ in which the slides or cover-glasses 

 to be stained have been placed. About twenty minutes 

 suffices for the differential staining, as shown in the plates, 

 to take place. The specimens are then washed in distilled 

 water till no more colour comes away, and are then allowed 

 to dry in the air. No heat must be used for drying, other- 

 wise the red colour Avill entirely disappear. They are then 

 mounted, preferably in turpentine colophonium, in which 

 the colours keep, according to our observations, for the 

 longest time. 



A"ai-ious other modifications of this method of staining have 

 been suggested by Noclit, Renter, Laveran, Leishman, and 

 others, but although they all give the specific reaction, we 

 have not found any which give so brilliant and clear a picture 

 as that described. 



2. The Appearances of the Adult Trypanosoma. — 

 When the preparation has been successful the appearances 



VOL. 45, PART 3. — NEW SERIES. H U 



