SPECIAL METHODS 
143 
Many fixing agents either destroy the mitochondria or make it 
almost impossible to demonstrate them. Fixing agents containing 
alcohol or any considerable percentage of acid are to be avoided. 
Benda’s solution, followed by Haidenhain’s iron-alum haematoxylin, 
will give good results. A solution recommended by Bensley is good 
also for plant material. 
Bensley’s Solution.— 
Osmic acid 2 per cent. 1 part 
Corrosive sublimate (HgCl 2 ) per cent. 4 parts ' 
Add 1 drop of glacial acetic acid to 10 c.c. of this solution. Fix 
for 24 to 48 hours and wash thoroughly in water. On the slide, 
bleach with hydrogen peroxide; wash in water; treat with the iodine 
solution used in testing for starch; then wash in water. The slide 
is now ready for staining. We recommend the usual Haidenhain’s 
iron-alum haematoxylin. 
Bensley recommends the following method which we have found 
rather uncertain, but which, when successful, yields magnificent 
preparationsOn the slide, bleach for 2 or 3 seconds in a 1 per cent 
aqueous solution of permanganate of potash; then treat with a 
5 per cent aqueous solution of oxalic acid until the preparation 
becomes white (a few seconds); wash in water, and then stain as 
follows: 
1. Copper acetate (neutral) saturated solution in water, 5 to 10 minutes. 
2. Wash in water. 
3. ^ per cent haematoxylin, 5 to 10 minutes. 
4. Wash in water. 
5. Potassium bichromate (neutral) 5 per cent solution in water until the 
preparation blackens, usually 30 seconds or less. 
6. Differentiate in Weigert’s ferricyanide solution. 
Borax. 2.0 g. 
Ferricyanide of potassium. 2.5 g. 
Water. 200.0 c.c. 
7. Wash in water and proceed as usual. 
CANALICULI 
By using special methods, Bensley has obtained views of the 
protoplasm of plants, quite different from those seen in ordinary 
preparations. In the cell of a root-tip a series of small canals, or 
vacuoles, appears, which is much more definite and extensive than 
