THE MICROTOMIST'S VADE-MECUM

paration is found to be coloured blue; a few      drops of a
solution of vesuvin are then placed on it, which has the        l
effect of discharging the methylen-blue from all the tissue-    1sb
elements, but not from the bacilli. The former are of 'a W'>
brown colour, and the blue bacilli are conspicuously defined." wi
The preparation is finished with absolute alcohol, oil of        tiO
cloves, and balsam. " This peculiarity of being rendered        ms RC
visible by the combined action of methylen-blue and vesuvin    ft 11
is possessed only by the tubercle-bacilli and by those -of      gE5
leprosy. All other bacteria and micrococci known to Koch        ol(s(I
lose, under the action of vesuvin, the blue colour which they    11
acquire from methylen-blue." I'
167. Staining Bacilli of Tuberculosis (Ehrlich's method'). 1eS
The alkali used in Koch's process " exercises a modifying       ths
action on the different histological elements and on the        grMa
bacteria themselves. . . . Ehrlich therefore sought for         Aiig
another base, acting in a less powerful manner, and found it    kfoie I
in )henylamin or anilin."                                     Coldi
A thin layer of expectorated matter is spread on a cover-
glass, dried, and fixed by warming for an hour at 1000 or       diD
120' C., or by passing rapidly four or five times through the    10.
flame of a spirit lamp. The cover is then floated with the       wIolhi
tubercular layer downwards, for a quarter to half an hour on qlissj
the surface of the staining fluid, which is prepared as          sdW
follows :un s(
" A saturated solution of phenylamin is to be made in dis-    1aial
tilled water, by shaking with the water the excess of anilin    ef1O'J
which floats on it, and carefully filtering the whole. To the merg
transparent liquid   thus obtained add, drop by drop, a          1aiuss
saturated alcoholic solution of fuchsin or methyl-violet until   Ifi
a slight opalescence is produced."  This is the first part of    ai
the process. The preparation must now be washed out, so as
to leave the bacteria alone stained. The cover is therefore
I' Bull. Soc. Beig. Micr.,' vii (1882), p. cxvii. ' Journ. Roy. Mic. Soc.'  ' us
(N.S.), ii (1882), p. 573.

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