ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
821 
I always add, before fitering, about 1/20 of a strong solution of 
thymol in absolute alcohol to the gum and glycerin (i.e. about one part 
of alcoholic solution of thymol to 20 parts of gum and glycerin 
solution). This, of course, precipitates some of the gum, but it soon 
becomes redissolved, and Farrant prepared in this way has kept sweet 
for many months. 
The use of the glass plate is, first, to exclude dust, and secondly, and 
chiefly, to prevent evaporation. 
((3) Staining with Picrocarmine. — In the histology courses at Oxford 
we use this stain very largely, as it is very convenient, easy to make, 
and preparations made with it are permanent. We stain the sections on 
the slide, remove some, hut not all, of the stain with blotting-paper, and 
mount in Farrant ; the surplus stain becomes mixed with the Farrant, 
but in a few days the section absorbs nearly the whole of it and as a 
result exhibits a better differentiation than can be obtained by any other 
means with which I am acquainted. I first saw the stain used in this 
manner by Professor Stirling, in the Owens College, Manchester. 
(y) Connective Tissue . — It is often difficult, in a class of histology, 
to demonstrate by means of the ordinary reagents the presence of con- 
nective tissue corpuscles in preparations of areolar tissue. 
The following method has been found satisfactory : — Snip out a small 
piece of the subcutaneous connective tissue of a recently killed rabbit, 
spread it upon the slide by means of two needles without the addition of 
any reagent, then flood it with absolute alcohol for about one minute, 
remove alcohol, stain with hsematoxylin, dehydrate, and mount in 
balsam. 
Excellent preparations may also be made with methyl-green, but this 
reagent is not usually supplied to students in a class, requires special 
skill in its use, and is not permanent. 
(8) AspinalVs Enamel . — As a cement for ringing slides and making 
cells Aspinall’s enamel has proved of great use. I have used it for some 
time and find that the white keeps well when used for balsam and 
Farrant mounts ; but I have not used it for a sufficient length of time 
to know whether it possesses any advantages over zinc white cement. 
The Differentiator.* — Mr. N. A. Cobb describes an improved form 
of the differentiator, or instrument for avoiding to the greatest possible 
extent those annoying and often destructive contractions which occur 
in delicate organisms while they are being killed and preserved. The 
instrument is made of glass tubing with an internal diameter of five or 
more mm. ; two forms are shown in figs. 103 and 104. a or a' is the 
reservoir, h the object-box, and c the filter ; these are three pieces of glass 
tubing joined by caoutchouc tubing. The filter is made by taking a 
piece of glass tube twice the required length, heating it red hot, drawing 
it out to arm’s length, and breaking in two in the middle ; the extremity 
should be drawn out very fine and a minute orifice alone left. 
Taking an example of objects fixed by corrosive sublimate which are to 
be studied in balsam after staining with borax-carmine, the author directs 
us to proceed as follows. Fill the filter with perfectly clean sublimate 
Proc. Linn. Soc. N.S.W., v. (1890) pp. 157-63 (1 pi.). 
