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THOMPSON YATES LABORATORIES REPORT 
2 Certain mixtures, which, when freshly made, cause the flagella to be thick 
and to stain deeply, after a time lose their power. This power is not lost all at once, 
but only gradually, and this declination is associated with an increasing fineness of 
the flagella and decreasing depth of colour. They become finer and finer, and more 
faintly stained, until finally they are no longer visible. At the same time the bodies 
of the organisms also become smaller, though they stain equally well. By none of 
the methods I have used have I succeeded in obtaining very fine deeply-stained 
flagella. When fine, they have always been faintly coloured and when thick more 
deeply dyed. 
3 If a ' mordant ' acted merely as a fixing agent, subsequent treatment with acids 
should have some effect. After using the ' mordant,' I have kept films in contact with 
Acid. Sulph. twenty-five per cent., Acid. Acet. ten per cent., and Acid. Nitric, ten per 
cent, for several minutes without any effect upon the subsequent staining of the flagella. 
If, however, spirit be used instead of the acids, the flagella can only be stained 
faintly, or are not visible. This later result might be used in support of the 
'precipitate' theory, the precipitate being soluble in spirit. But it does not invalidate 
the theory of ' thickening,' as the spirit may cause shrinkage by dehydration. The 
method used in these experiments was the following : 
(a) De Rossi's potash tannic acid. Tannic acid twenty-five per cent., 
dissolved by heat in one per cent, solution of caustic potash in 
water. This is saturated with fuchsin. 
(b) Perchloride of iron ten per cent, dissolved in water + five per cent. 
glacial acetic acid.* 
(c) Water + five per cent, glacial acetic acid. 
The films are made in the usual way, allowed to dry in the air, and then 
exposed to formalin vapour for about half an hour. 
Equal parts of (a) and (b) are mixed in a test-tube, and boiled. Then an equal 
bulk of (Y) is added, the whole shaken up and filtered twice. This mixture is allowed 
to remain in contact with the film for a time, which varies with the organism used and 
the result required. From two to seven minutes is a good time for B. typhosus. 
The cover slip is then well washed in water (treated with acid if preferred, and 
washed in water), and stained for about ten minutes in a warm solution of one of the 
ordinary dyes (an alcoholic-aqueous, one to four or weaker solution of gentian violet 
gives good results), well washed, dried and mounted in balsam. 
The ' mordant ' retains its properties for a few hours only. 
In specimens stained by this process the protoplasm of the organisms is 
somewhat enlarged. In many cases the protoplasm appears to be surrounded by 
a ' capsule,' or ' thickened cell membrane,' which may or may not be stained. t 
* This solution seems to lose its power atter a few days. 
f C.f. Bacterial. Diagnost., Lehmann and Neumann, Vol. II., p. lS. 
