ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1063 



to give a definite opinion of its value, but he thinks tliat it will be found to 

 be extremely useful. 



Directions for using Prof. H. L. Smith's High Refractive Mounting 

 Media.* — Prof. H. L. Smith gives the following directions : — Use barely 

 enough of the medium to fill in under the cover when the slide is warmed ; 

 it does not materially diminish by any subsequent heating. 



Boil thoroughly under the cover and until all bubbles disappear on 

 allowing the slide to cool ; if any should still remain they may be readily 

 coaxed out by proper application of a small flame. 



When the slide is cold the cover should remain firmly fixed ; any excess 

 of the medium must be removed by means of a moist cloth or a roll of 

 moistened tissue paper. The cleansing must be thorough ; all excess must 

 be removed around the edge of the cover, as otherwise it is liable to act 

 upon the cement or finishing ring. If, after the cleaning, the cover shows 

 metallic stains, do not attempt to clean them off until after the finishing 

 ring is hard. When the excess has been removed around the edge of the 

 cover, gently warm the slide to drive oft' the small amount of moisture that 

 may have been absorbed during the cleaning. When again cooled apply a 

 protecting ring of asphalt-black, or white zinc, or, perhaps better, if one 

 will take the trouble to make them, a wax ring, punched from the sheet- 

 wax used for artificial flowers. The wax ring is a sure protection, especially 

 for the highest medium, yet the white zinc or the asphalt answers well. 

 In using the wax ring, the heat must be very cautiously applied, so as 

 barely to melt it, following gently around with a very small flame. If 

 bubbles of air are entangled under the ring, touch them with a heated 

 needle-point just before the wax cools. 



When the asphalt, white zinc, or wax ring is solid, apply a good coat 

 of shellac dissolved in alcohol. Slides thus protected keep perfectly well. 

 After the ring is firmly set, any metallic stains remaining on the cover 

 may be removed by a piece of tissue paper and moistened with hydrochloric 

 acid. 



Section-lifters. | — Dr. W. Y. Cowl advocates the use of section-lifters 

 made of horn. They are in one flat piece, weigh 10 grains, are 3 in. long, 

 and 5/8 in. wide at the blade, which is square, of about ] /200 in. thick, 

 and merging into a handle 1/20 in. thick and 3/8 in. wide. The blade is 

 smooth, flexible as paper, and pierced with fine holes. It can thus be 

 insinuated beneath a section lying flat on the bottom of a dish and upon 

 removal from the surrounding fluid will allow it to drain away from 

 between the section and lifter. This brings the two into uniform apposition, 

 which is a great desideratum. The perforations also favour the floating 

 of the section from the lifter to the mounting or preparatory fluid on the 

 slide. As horn normally contains grease as well as moisture, it will take 

 oily or gummy media, but must then be confined to use with them. Lifters 

 for water or glycerin must be made of burnt horn, i. e. mostly deprived 

 of fat. In preparing specimens, the lifter is preferably inverted over the 

 slide when loaded with a section, whilst a drop of fluid let fall on the holes 

 in the middle of the blade, loosens the tissue, from which the instrument may 

 then easily be withdrawn. As the horn is transparent, every detail of the 

 section on its under side can be seen. 



The use of such a section-lifter naturally suggests a stout bristle 

 instead of a needle. It may be held in a clamping needle-holder, and when 

 so moimted, or even simply tied to a stick, will so far surpass the needle as 

 a means of manipulation that no one who has ever tried it will cease its use. 



* Microscope, vii, (1887) pp. 308-9. t Ibid., pp. 1G4-6. 



