45 
Time Required for Fixation .—This varies according 
to the size of tissues and fixative, but the necessary time 
can always be determined by cutting through one of 
the pieces. If the tissue is opaque throughout, it is 
a sign that fixation is complete. The tissue should then 
be removed and washed. (Vide ch. xxxiv.) 
Embedding Apparatus .—A slab of metal (copper), 
12 x 3 x J inches. Heat this at one end, and place 
the vessel containing the paraffin at a point on the 
slab where the paraffin is just kept melted. This is 
the temperature for embedding. This simple device 
serves all the purposes of an elaborate paraffin oven 
(Fig- 12)- 
Microtome .—The Cambridge rocking microtome 
(£5), or the Minot (£12) are the most convenient, but 
sections can be quite well cut with cheaper instruments, 
e.g., the Jung {£I ios.). 
Razors .—These may be hollow-ground on one 
side, or on both, to a varying depth. For general 
use a moderately hollow-ground razor is used. Examine 
the edge under a low power to see if any notches exist 
if so they must be ground out on a hone. A Belgian 
stone, as long as possible, should be used and kept free 
from grit during use. The stone should be soft, 
