138 Brown: WooDs FOR MICROSCOPIC STUDY 
1. Cut chips to expose a radial length of 2 cm., an axial length 
of I cm., and a tangential thickness of 2 mm. 
2. Place these in a numbered test tube, cover with water, 
and keep at boiling temperature in the water bath for about an 
hour. The hot water is then replaced by fresh cold water and 
the tube reheated. Alternate cooling and boiling periods should 
be continued for at least five changes. 
3. Cover the material with 50 per cent nitric acid and add a 
small amount of potassium chlorate (as much as may be taken 
upon the point of a small knife blade). It is now kept at boiling 
temperature until the pieces have whitened and commenced to 
fray, when cold water is poured on, causing the macerated material 
to settle. The acid solution is then replaced with water and al- 
lowed to heat with the purpose of removing the acid solution. 
4. Transfer the material to a watch-glass where it may be 
teased apart with a small size artist’s brush. By means of a 
pipette, change the water several times or until all particles of 
foreign matter and traces of chemicals have been removed. 
5. Replace the water by 95 per cent alcohol for 30 minutes or 
until all air has been removed from the cell-lumina. 
6. Replace the alcohol by a 2 per cent solution of Bismarck 
brown in 70 per cent alcohol, in which the material should stand 
for twelve to twenty-four hours. 
7- To remove excess stain, wash quickly in alcohol and transfer 
to glycerine, which should be changed if greatly colored by the 
stain. 
8. Mount in glycerine and cement with Brunswick black or 
gold size. 
Preparations such as these are almost essential for the working 
out of the details of vascular anatomy. If a water bath capable 
of receiving twenty test tubes is used, but little time need be 
consumed in making the preparations. The action of the chemi- 
cals proceeds so slowly that there is little danger of tissues being 
destroyed. 
5. DEFINITION OF ANATOMICAL DETAILS 
A. BY DIFFERENTIAL STAINING 
In the writer’s experience, Haidenhain’s iron-haematoxylin 
has proved the best all-round stain for bringing out the anatomical 
