72 
Laboratory Notes. 
convenient, stains dissolved in alcohol may be used ; but greater 
care is necessary, for the alcohol may catch alight, and also the 
sections shew a tendency to wash off the slide. 
The method opens up many questions regarding the physical 
chemistry of staining ; for instance, why should sections embedded 
in paraffin stain so much more quickly than when the wax is removed. 
Of course, a hot dye will stain more quickly than when cold, but 
the increase in temperature does not by any means entirely account 
for the phenomenon in the above method. It is possible that the 
mode of presentation of the dye is important: the solid paraffin 
consists of innumerable crystals separated one from the other 
by very minute capillary spaces, so that when the microtomed 
ribbon is floated on the solution of the stain, the pigment is presu¬ 
mably presented to the tissues in innumerable capillary columns. 
Has this, if true, anything to do with the phenomenon ? 
It may also be noted that many dyes, safranin for example, 
stain the tissues generally, not merely the lignified and cuticu- 
larized walls only. T. G. HILL. 
Scharlack R: A Microchemical Test for Oils. 
The usual microchemical reagents for oils are osmic acid and 
tincture of alkannin : both are unsatisfactory, the former is expen¬ 
sive, does not keep any length of time and stains other reserve food- 
materials in addition to the oils; the latter to give entirely satisfactory 
results should be freshly prepared from the root of Alkannn tinctorm, 
which is inconvenient. 
While working at St. Thomas’s Hospital it was noticed that 
sections of certain pathological tissues, (amylosis of the liver?) 
were stained with Scharlack R. to contrast the particular feature. 
On trying this reagent with many oil-containing seeds, e.g., sun¬ 
flower, hemp, castor oil, etc., it was found that the oil globules 
speedily absorbed the dye and were stained a bright pink ; in fact, 
it appears an excellent reagent, has been used in my practical 
classes for several years, and has never failed. So far as has been 
seen it does not deteriorate with age ; further, it is easy to make up 
and its reaction is characteristic. To prepare it, make a saturated 
solution of the solid stain (Griibler’s) in a mixture of 70 parts of 
absolute alcohol and 30 parts of water by volume. When the 
solvent will take up no more stain, filter and keep in a glass 
stoppered bottle. For use, mount the section, or the scraping of 
the seed, in a drop or two of the Scharlack R. In a very short time 
the stain will all be absorbed by the oils which will be coloured a 
bright pink: Protein bodies and starch grains are unaffected, and, 
with regard to membranes, cellulose and lignified walls remain un¬ 
stained whilst cuticle stains a bright pink. 
Sudan 111 similarly prepared and used will give like results. 
T. G. HILL. 
