ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 121 



about 24 minutes, and few or none are ever spoiled in the process, which 

 is as follows :— 1. Prepare a solution of 1 p.c. celloidin in absolute alcohol. 



2. A solution of celloidin (5 p.c.) in absolute alcohol of the consistence 

 known as "thick" in ordinary histological work. It is essential that 

 no ether be employed in the solution, as it makes the scales transparent. 



3. Catch the mosquito. 4. Chloroform it. 5. When dead or narcotized, 

 place a drop of solution No. 1 — thin celloidin — on a cover-glass. 6. 

 Place the insect back downwards on the cover-glass. In the majority of 

 cases wings and legs spread themselves out in the orthodox exhibition 

 position. If they do not do so the solution remains fluid sufficiently 

 long in Bombay at a temperature of 85° F. to 1)0° F. for from 3 to 5 

 minutes to permit them to be adjusted with a needle. 7. When the 

 thin solution has become " tacky," to use the language of the motorist — 

 i.e., in about 8 or 10 minutes from the commencement of operations — 

 place a drop of the thick solution, No. 2, over the insect. 8. Invert 

 the cover-glass over a hollowed slide, to which it may be fixed by a ring 

 of balsam. The specimen is now complete, and in this condition both 

 ventral and dorsal surfaces can be examined under the Microscope. 



If it be thought desirable to employ a white background, instead 

 of manoeuvre 8 proceed thus : — 8a. Suspend some oxide of zinc in 

 ordinary mounting Canada balsam. Shake or stir well immediately 

 before using ; fill the cell or hollow of the slide with this emulsion ; 

 invert the cover-glass with the mosquito, and press rather firmly into the 

 emulsion. 9. Clean off any of the emulsion that spreads beyond the 

 edge of the cover. Specimens prepared by this latter method will, of 

 course, display only one surface. 



Celloidin in Microscopical Technique.* — L. Neumayer has found 

 that celluloid in plate form may be found useful as slides or coverslips. 

 The best material is practically as transparent as glass, and can be 

 obtained in any size and thickness. In this connexion it may be recalled 

 that mica and gelatin have also been used instead of glass. The inflam- 

 mability of celluloid must be taken into consideration ; in other respects 

 it seems that celluloid is a convenient substitute for vitreous plates. 



Microscopical Examination of Foods and Drugs. — This work, by 

 H. G. Greenish,! is a practical introduction to the method adopted in 

 the microscopical examination of foods and drugs in the entire, crushed 

 and powdered states. It has deservedly reached a second edition.! Its 

 principal features remain unaltered, though certain revisions and addi- 

 tions have been made. Among these may be mentioned the chapter on 

 fibres, saffron, liquorice, calumba, etc. A chapter has been added on 

 the more commonly occurring adulterants of powdered foods and drugs. 

 A new section consists of a general scheme of examination which will 

 be found specially useful in the investigation of an unknown powder. 



Drop-bottle for Preventing the Action of Air on Copper-oxide- 

 ammonia Solution. § — G. Herzog describes a drop-bottle which he has 



* Zeitschr. wiss. Mikrosk., xxvii. (1910) pp. 234-8. 



t London : J. and A. Churchill, 1910, xvii. and 386 pp. (209 illus.). 



i See this Journal, 1903, p. 561. 



§ Zeitschr. wiss. Mikrosk., xxvii. (1910) pp. 272-4 (1 fig.). 



