54 
Wager and Penis ton.—Cytological Observations on 
produces a beautiful general cytological stain. Useful results similar 
to those obtained with potash alum have been obtained by mordaunting 
for half an hour in a 3 per cent, solution of ferrous ammonium sulphate, 
staining in the haematoxylin for two hours, and then decolouring in 
a solution of ammonium alum. 
We do not find that contrast stains add to the clearness of preparations 
stained with Heidenhain’s haematoxylin, and in many cases they tend 
to obscure the finer cytological details. Some excellent results have, how¬ 
ever, been obtained by first staining in safranin (1 per cent, solution in 
70 per cent, alcohol), and then proceeding as usual with the haematoxylin 
staining. Useful results have also been obtained by staining for a few 
minutes in methylene blue, or the methyl green-fuchsin mixture, after the 
final washing of the differentiated haematoxylin preparations. 
Brazilin has been substituted for haematoxylin and gives similar 
results. It has, however, the disadvantage of requiring a much longer time 
to stain. Good preparations have been obtained by using 70 per cent, 
alcoholic solutions throughout. 
Delafield’s haematoxylin and Mayer’s haemalum are useful general 
stains, but tend to be diffuse. Haemalum has the advantage of differentiating 
the volutin granules. The best results in both cases are obtained by over¬ 
staining, and subsequently differentiating in acid alcohol. 
Methyl green and acid fuchsin is very useful for temporary prepara¬ 
tions ; 2-5 minutes in a mixture of equal parts of 5 per cent, solution 
of methyl-green and acid-fuchsin produce a beautiful differential stain, 
which stains the volutin as well as the chromatin granules. Permanent 
preparations can be obtained by staining 3-10 minutes in the mixture, then 
immediately washing in 90 per cent, alcohol and dehydrating rapidly. 
Clearing in clove oil enhances the brilliance of the stain, and extracts any 
excess of methyl green, but the clove oil must be washed out with xylol, or, 
better still, replaced by cedar oil. Such preparations mounted in neutral 
Canada balsam will keep well, if not unduly exposed to sunlight. 
Methylene blue and acid fuchsin produce an even more beautiful stain 
than methyl green and fuchsin, when mixed in the right proportions. 
Methylene blue has been used for the detection of volutin. We have 
found a 1 per cent, solution most useful. To obtain permanent preparations, 
it is necessary to stain for about two hours in this solution. 
Safranin alone does not give good results, but in combination with 
gentian violet produces useful and brilliant staining. The preparations are 
stained eight hours or overnight in a 1 per cent, solution of safranin in 
70 per cent, alcohol. They are then washed in alcohol and water and 
transferred to a 1 per cent, aqueous solution of gentian violet for 3-10 
minutes. Dehydration must be carried through quickly, and any excess of 
gentian violet extracted by clove oil, which must be replaced by cedar oil. 
