ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 87 



they turn blue again ; and then follow dehydration in absolute alcohol, 

 xylol, balsam. Under the Microscope the parasites are stained red, and 

 exhibit their characteristic appearance while the nucleus and cytoplasm 

 are blue. 



(5) Mounting-, including' Slides, Preservative Fluids, etc. 



Use of Glycerin-jelly in Mounting Microscopical Objects.f 

 L. W. Stansell, after remarking that mounting with this medium is quite 

 simple, gives the following procedure :— The jelly in the stock-bottle is 

 allowed to become liquefied by standing in the water-oven ; should it 

 contain air-bubbles, time must be given for these to rise and escape. A 

 few clean 3-in. by 1-in. glass slips are ready upon a flat bench ; then, with 

 a glass rod, one drop of the limpid jelly is carefully placed on the centre 

 of each slide, the drop not being allowed to fall from the glass rod, but 

 almost placed in position. The drop of jelly soon sets to a clear, lens- 

 like form, usually free from air-bubbles. Should one, however, be seen, 

 it can be dispersed with a warm needle, or else by the same means drawn 

 to one side and pushed out of the way before the jelly sets. These 

 prepared slides are ready for immediate use, or if preferred they can be 

 stored in a bos out of the dust for some days until wanted. It is 

 important to have objects for mounting in the moist condition ; particles 

 of fibre from feeding-stuffs will already be in that state if the material 

 has been prepared for the determination of cellulose ; they can be taken 

 direct out of the final washing water. Portions of dry leaves, mosses, 

 and similar structures are soaked for some days in a preservative fluid 

 consisting of distilled water 2 parts, rectified spirit 1 part, and glycerol 

 1 part. Each specimen is kept in a small bottle or tube with a little of 

 the fluid ; it gradually penetrates and will displace the air, more speedily 

 if put in a warm place. Some tissues previous to this soaking may even 

 be boiled in distilled water and allowed to remain there till cold. The 

 air-free water helps to dissolve out residual air. A simple method of 

 preparation to employ for leaves — tea, for instance — is to raise cautiously 

 to boiling in a test-tube with dilute nitric acid, and then freely dilute 

 with water. If the structures float owing to imprisoned air, further 

 boiling in water is necessary before proceeding to wash. The cuticle 

 separates and can easily be stripped off. The fragments of husk, cuticle, 

 etc., are taken while wet and gently laid with forceps upon the flat bead 

 of solid jelly, the excess of water or other fluid allowed to drain off for a 

 moment, and then the slide slowly warmed over a very small flame. The 

 jelly melts, and the object in situ will sink into the liquid jelly without 

 as a rule the introduction of a single air-bubble. The cover-glass is 

 applied and gradually lowered, placing a flattened bullet on it to keep it 

 in position, then left for some minutes till the slide has set. Not much 

 pressure should be exerted, or the cover-glass may have a tendency to 

 spring up afterwards. At this stage the mount admits of microscopical 

 examination. When this is completed, the processes of finishing the 

 slide can be proceeded with, or, if desired, held over, and the slide 

 reserved for treatment with others. Sediments and other finely divided 



* Journ. Soc. Public Analysts, September 1913. 



