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SYDNEY J. HICKSON. 
fumes. This is done in the following manner. The sections 
are fixed in position on the slide by Meyer’s albumin and 
glycerine solution, and when the paraffin has been removed by 
turpentine and the turpentine driven off by absolute alcohol, 
the slide is inverted over a capsule containing 90 per cent, spirit, 
to which a few drops of strong nitric acid have been added. 
Copious nitrous fumes are given off and the pigment dissolves. 
The action can be stopped at any moment by washing with 
neutral spirit and when the washing is complete the sections 
can be stained in haematoxylon or any other solution. 
For teasing the best solution is chloral hydrate. I leave the 
eye or optic tract in a 5 per cent, solution of chloral hydrate for 
twenty-four hours, and then tease with needles and mount in gly- 
cerine. In some cases I have made very satisfactory preparations 
by fixing the teased tissues to the slide with albumin and gly- 
cerine solution and then washing with spirit and staining in the 
ordinary way, or staining after depigmenting with nitrous fumes. 
I have tried various kinds of haematoxylon stains, but the 
solution which gives the best results, and is in every way the 
most satisfactory, is one which 1 have made by following 
Mitchell’s (16) instructions, with a few additional precautions. 
I will describe here the mode in which I now make haema- 
toxylon stain. 
Take 56 grammes of the logwood extract and thoroughly 
pound it in a mortar. Then place it on a filter, and pour 
about a litre and a half of ordinary tap water through it. The 
filtrate may be thrown away and the residue allowed to dry. 
In the meantime prepare a solution of alum as follows : — Take 
25 grammes of alum, and after they have been thoroughly 
pounded in a mortar pour them into 250 cc. of distilled water. 
To this solution add strong potash until a precipitate is formed, 
which will not dissolve upon stirring and standing. 
Pour the alum solution thus made on to the haematoxylon 
residue, and allow them to macerate together for three or four 
days in a warm room. Then filter the haematoxylon solution 
into a bottle provided with a closely-fitting stopper, and add 
to it 10 cc. of pure glycerine and 100 cc. of 90 per cent, spirit. 
