ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
293 
yellow, the connective tissue a pale green, elastic fibres violet, and 
cartilage yellow. 
If it be desired to stain micro-organisms at tho same time as tho 
tissues, the sections are, after having been stained with carmine, de- 
colorized by Gram’s method, or by the Koch-Ehrlich method for tubercle 
bacilli, and then are immersed for five minutes in the aqueous solution of 
picro-nigrosin, after which the process terminates as above. 
( 5) Mounting', including: Slides, Preservative Fluids, &c. 
Combined Method for fixing and flattening Paraffin Sections.* — 
Mr. H. E. Durham has devised a modification of Canini’s method in 
which alcohol is used as a means of causing sections to adhere to a slide. 
These sections are placed on a dry slide or are moistened with ordinary 
methylated spirit diluted to 70 per cent, alcohol. The slide is placed 
on a horizontal metal plate kept sufficiently warm to soften the paraffin. 
More alcohol is run on by means of a pipette. As the slide becomes 
warm the paraffin softens, and any little wrinkles disappear, the sections 
floating flat on tho top of the alcohol. When they all appear flat the 
excess of alcohol may be removed with a pipette. 
When all the alcohol has evaporated, the paraffin may be just melted 
and then dissolved with benzol or xylol. Canada balsam may then bo 
dropped on and the cover-glass applied, or the slide may be put through 
absolute alcohol, and stained and mounted as desired. 
Care must be taken that the warm plate is not too hot, for if tho 
paraffin melts completely the sections are unsupported. It is claimed 
for the method that it is much less troublesome than Gaskell’s, and quite 
as satisfactory for even apparently hopelessly crumpled sections. 
More about Cements, f— Mr. J. D. Beck remarks: — “Invaluable 
articles have been written on the nature of cements and varnishes for 
finishing mounts. I feel my incompetence to enter a field among superior 
microscopists with my suggestions, except on important points, which, in 
my opinion, have been overlooked, as I do not recollect to have read 
any comments as to the applying of anything on top of the cover-glasses 
of mounts. For objectives of low power this answers very well, if it is 
a good, hard, and elastic varnish or cement, fixing the cover-glass 
securely, but when it is desirable to use high power objectives of short 
working distance, these rings, thus applied, are in the way of the lens, 
which is more or less liable to injury by contact with the ring of varnish 
on the cover. I perceive, however, as 1 look over my collection of slides, 
that many microscopists never or seldom allow any cement or varnish to 
rise above the upper smface of cover-glasses. This effectually 
prevents all trouble with high power objectives, unless the cover 
is not parallel with the slide, a very common annoyance, but it does 
not hold the cover as securely as a thin coat of hard and elastic 
finishing varnish applied around tho edge with a very narrow ring 
on top, being sure that there is no break between the ring at the edge 
and that at the top. 
Many cements have been prepared and are in the market which are 
* Quart. Journ. Micr. Sci., xxxiii. (1831) pp. 116-7. 
t '1 lie Microscope, xi. (1891) pp. 338-41 ; 86S-70. 
