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PROGRESS OF MICROSCOPICAL SCIENCE. 
Double Staining with a Single Fluid. — Iu the ‘American Journal 
of the Medical Sciences ’ for January last, there is a long and interest- 
ing article by F. Merbel on the double staining of tissues by a single 
fluid. Many similar fluids have been tried before, but have not 
realized the hopes that were entertained regarding them, that in a 
complex tissue the various constituents should show a marked selec- 
tion for the different colours or tints, which should be constant, and 
might serve to afford some additional evidence as to their structure. 
That such a stain has not yet been discovered may be asserted, nor 
does the author iu his paper claim to have arrived at this result, but 
he appears to consider that by some modification of his process, the 
uncertainty and failure may be eliminated and a successful result be 
always obtained. The stain consists of two fluids which are mixed 
before using. One consists of half a drachm of carmine, two drachms 
of borax, and four ounces of distilled water ; tbe other, of two drachms 
of indigo-carmine, two drachms of borax, and four ormces of distilled 
water. The ingredients should be very carefully rubbed in a mortar, 
and after standing for some time the supernatant fluid must be poured 
off, filtered, and kept in a stoppered bottle. They are to be mixed in 
equal proportions. The sections or tissue to be stained should be as 
thin as possible, and if they have been hardened in chromic acid or 
chromates, all traces should be removed by careful washing, they may 
then bo plunged for a few minutes in alcohol, from which they are 
transferred to the staining fluid ; after remaining in this for a quarter 
of an hour or twenty minutes they are removed to a saturated solution 
of oxalic acid for a rather shorter period, and are then washed in 
distilled water till no trace of the acid remains. They may then be 
treated in the ordinary way and mounted in Canada balsam, glycerine, 
jelly, &c. Indigo-carmine is the commercial name for the sulphindigo- 
tate of potassium or sodium, and as this is very soluble in water the 
oxalic acid is used with the object of fixing it ; unfortunately this 
acid precipitates carmine, and this is, without doubt, tbe weak point 
in the combination, nevertheless some very good results have been 
obtained, and a successful preparation is a most beautiful object. 
There is not only the blue of the indigo and the red of the carmine, 
but different shades of purple, violet, &c., and in a structure that has 
been decalcified in chromic acid, a phalanx for instance, if some trace 
of the acid remains a series of greens make their appearance. In a 
section of ecchymosed skin the extravasated blood-disks presented a 
brilliant apple-green tint ; indeed at first sight so varied is the colour 
that one would more readily believe it was due to polarized light than to 
the action of a single staining fluid. Whether a fixing .agent other than 
oxalic acid, and which shall not act deleteriously on the carmine, can be 
substituted, must be the result of future investigation and experiment. 
The Minute Structure of Bed Blood-corpuscles. — In the ‘ Archiv. 
fiir Mic. Anat.,’ Bd. 14, Professor Boettcher gives the results of some 
continued researches on the structure of the red blood-corpuscle. 
