MICROSCOPICAL TECHNIQUE, ETC. 1 69 
This is not the place for us to go at great length 
into staining processes ; nor is it necessary, for sections 
well stained by any process will yield good photographs. 
The well-known picro-carmine, for example, is excellent 
for photo-micrographic purposes, but it will not be 
amiss to describe what seems the best process for our 
special work, leaving out notice of special microscopic 
researches, such as those into cancer-parasites, specific 
chemical reactions, etc. 
Ehrlich ' 1 s Acid Hcematoxylin .—Haematoxylin one and 
a half grammes dissolved in absolute alcohol 100 cc., 
add glycerine and distilled water each ioo cc., glacial 
acetic acid io cc., and potash alum to excess. Allow 
to stand in a light place for some weeks. The older 
this is the better, but it must be red and not purple in 
colour. If it becomes purple add acetic acid. This 
should stain nuclei in about five minutes, or ten at the 
most. If in place of haematoxylin hcematein is used, the 
solution will be ready for use much sooner; and if this 
haematein is diluted to such an extent that it stains 
thin sections in about eighteen to twenty-four hours we 
shall have perhaps the most exquisite nuclear stain in 
existence. If it is not intended to counter-stain, or if 
absolute discreteness is not necessary, the preparations 
are washed in tap water directly from the stain ; but if 
we propose to stain other elements besides nuclei, the 
sections must be washed in distilled or acidulated 
water, and then in tap water till they take a true blue 
colour. If the tap water is not distinctly alkaline, a 
little alkali may be added to it; the alkali fixes the 
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