Tue Microscope. 125 
should be selected that can be used either as a freezing-micro- 
tome orsimply asa more common well-microtome. This pattern 
should also hold the knife in a suitable frame, so attached to 
the microtome that all movements of the knife may be abso- 
lutely free and easy. To use these superb instruments it is only 
necessary to attach the tissue to a piece of cork with some gum 
solution and proceed at once to cut the sections. If the tissue 
be soft and fresh then a few moments suffice to freeze it hard 
with the ether spray. If the tissue be already hardened then as 
soon as the gum has hardened sufficiently to hold the tissue to 
the cork the section-cutting can commence. It is better to at- 
tach several of the hardened pieces of tissue to corks with the 
eum solution at one time and then place them in the bottle of 
alcohol to be used at pleasure. The cork only is placed in the 
clamp of the microtome while the superimposed tissue is left 
free for the knife. There is no embedding mixture of any kind; 
the edge of the knife is entirely free from contact with every- 
thing except the tissue, hence never gets injured; the instru- 
ment is sO ee graduated rach sections ¢ can be cut very rap- 
is Bales Bade Sail Limaye clear 
EMBEDDING MIXTURES. 
Solid paraflin, 3 parts 
Cocoa butter, 1 part soft. 
Hog’s lard, 3 parts 
Solid paraffin, 3 parts 
Cocoa butter, 2 parts hard. 
Spermaceti, 1 part 
Solid paraffin, 2 parts 
Cocoa butter, 1 part harder. 
Spermaceti, 1 part 
Paraffin, 2 parts ) 
Vaseline, 1 part § 
These are very common mixtures for embedding although 
Cole, of London, recommends them only to * those who are fond 
of messes, and the method is mentioned only to condemn it as 
unnecessary and dirty in every way.” Notwithstanding this 
terrible denunciation, the method of embedding with paraffin 
will continue to occupy its position as an easy way of holding a 
tissue firmly in place without injury to it or to the knife. 
Transparent and easy to cut. 
