690 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cutting. Instead of squeezing the two — cork and block — together, they 
may be fused firmly by immersing them in 60 per cent, spirit for about 
a day. All the foregoing steps are to be carried out in glass vessels, but the 
formation of the section block by pouring a thickish solution of celloidin 
into paper cases, and then, having properly oriented the object, hardening 
the mass by immersion in 60 per cent, spirit, is also advised. In any 
case the consistence of the celloidin block should be about equal to that 
of cartilage. 
In sectioning an object imbedded in celloidin, it is necessary to 
use an immersion microtome, or, at any rate, to employ some means for 
keeping the knife moist. This may be effected by a dropping apparatus 
filled with 60 per cent, spirit. It is not at all necessary to remove the 
celloidin from the sections, and these, after they have been mopped up 
with blotting-paper, are easily made to adhere to the slide by exposing 
them to ether vapour. 
The further treatment of the sections depends on whether they are to 
be mounted in an aqueous or resinous medium. In the former case the 
dilute spirit is removed by immersion in water ; in the latter by treating 
them with 90 per cent, spirit. The author’s remarks on paraffin mostly 
refer to the treatment of sections which have been imbedded in paraffin. 
He advises that all manipulations should be carried out on the slide on 
which the sections are to be deposited on removal from the knife. The 
technique of these steps is, of course, the same as that usually adopted ; 
the paraffin having been dissolved out, the ultimate treatment] of the 
section will depend on the character of the medium in which the section 
is to be mounted. The mounting medium may be aqueous or resinous, 
and if the former, then it may remain fluid (acetate of potash, chloride 
of calcium solution), or may set (glycerin jelly), while resinous mounts 
require the preparation to be dehydrated. Hence the effect on the 
section will vary much, and, therefore, which course of the three should 
be adopted must be decided by the nature of the tissue in the section. 
Different kinds of mounting media are then passed in review and the 
first mentioned are chloride of calcium and acetate of potash, both of 
which are pronounced to be suitable for delicate parenchyma and for 
tissues rich in protoplasm, but the use of these fluids is to be avoided, 
owing to the extra trouble such preparations involve. Glycerin jelly 
receives commendation, as it may be used for stained objects, does not 
require to be perfectly cleared, nor to be ringed round. Media, the 
principal constituent of which is gum, are then discussed : of those 
noticed maybe mentioned Farrant’s medium (of which the author admits 
his practical ignorance) and Hoyer’s media, one of which, made of 
gum, chloral hydrate, and glycerin, is intended for preparations stained 
with logwood and carmine, while the other is composed of gum and 
acetate of potash solution. Both these fluids are of the consistence of 
thick syrup, and as they dry at the edge, ringing round the cover-glass 
is not necessary. 
Besinous mounting media are colophonium, dammar, and balsam, 
the first two of which are best dissolved in turpentine, as too volatile 
solvents are inadmissible on account of the crystalline structure of these 
resins. Colophonium does not appear to possess many advantages, 
although one may be mentioned : it is little sensitive to a residuum of 
