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the Microscope and Food Adulteration. 43 
it is quite conceivable that some microscopical test might be 
found, based upon these distinctions. 
The presence of crystals or fragments of alum in flour may be 
rather prettily demonstrated by moistening a little of the flour 
on a slide with a mixture of tincture of logwood and carbonate 
of ammonia solution. A microscopical examination then shows 
a slaty blue patch on a pink ground wherever there was originally 
a fragment of alum. 
Much may be done with the microscope in the recognition of 
definite crystalline forms and characteristic crystal groupings ; 
these are of some help in the identification of alkaloids. Weare 
accustomed to think of crystals as hard, yet so soft a substance 
as butter readily takes a crystalline shape, and, indeed, its 
crystals are to a certain extent, and especially when viewed by 
polarized light, characteristic of the substance. If butter be 
melted and allowed to cool, its appearance is quite altered; it 
becomes glistening from the breaking up of light from its in- 
numerable crystal faces. When we find such crystals in butter, 
we have proof that it has been melted, and a suspicion may be 
aroused of admixture, while melted, with other fats, which sus- 
picion may, or may not, be confirmed by subsequent chemical 
analysis. 
‘* Dr. Thomas Taylor (of the U.S. Department of Agriculture) ”’ 
(I quote from J. P. Battershall) ‘‘has made an elaborate investi- 
gation of the microscopic appearance of various fats when viewed 
by polarized light. He regards the presence of peculiar globular 
erystals and the black cross commonly termed St. Andrew’s cross 
as characteristic of genuine butter. Lard, beef, and other fats 
are said to exhibit different and, to some extent, distinctive 
erystalline forms. Prof. Weber, however, affirms that mixtures 
of lard and tallow fat, under certain conditions, cannot be dis- 
tinguished from butter by means of this method of examination. 
More recently, Dr. Taylor states that the distinguishing difference 
between butter and other fats under the microscope is, that the 
former, when observed by polarized light through a selenite, 
exhibits a uniform tint, whereas the latter shows prismatic 
colours. Although the results of these investigations cannot 
as yet be considered as perfectly satisfactory or conclusive, they 
certainly are entitled to rank as a highly valuable and important 
step in advance of the optical processes hitherto employed.” 
Quantitative determinations by methods of counting under the 
microscope are in some cases possible. Speaking of the application 
of such methods to starches, A. W. Blyth says: “If adulteration 
in any case has been made out, approximative quantitative results 
may be obtained by making a standard mixture of the genuine 
starch with the adulterant found, and then counting the indi- 
vidual grains in the microscopic field. Thus, for example, 
