EXAMINATION AND I'll US mi VAT [ON MKDLA. 241 



liquid preserves the colour of preparations stained with anili/i 

 dyc-s, methyl green included. 



427. Levulose is recommended by BEHRENS, KOSSEL u. SCHIEF- 

 FERDECKEB (Das Mikroskop, etc., 1889). It is uncrystallisable, and 

 preserves well carmine and coal-tar stains (ha3inatoxylin stains fade 

 some what in it). The index of refraction is somewhat higher than that 

 of glycerin. Objects may be brought into it out of water. 



428. A MANN'S Lactophenol (from LANGERON, C. R. Soc. Biol., 

 Iviii, 1905, p. 750). Carbolic acid, 20; lactic acid, 20; 

 glycerin, 40; water, 20. For Nematodes, Acarids, etc. 

 Add gradually drop by drop to the water containing the 

 organisms. Not for mounting. Mount in glycerin jelly. 



Glycerin Media. 



429. Glycerin. Glycerin diluted with water is frequently 

 employed as an examination and mounting medium. Dilution 

 with water is sometimes advisable on account of the increased 

 visibility that it gives to many structures. But for efficacious 

 preservation undiluted glycerin, the strongest that can be 

 procured, should be used (see BEALE, How to work, etc.). 



For closing glycerin mounts, the edges of the cover should 

 first (after having been cleansed as far as possible from super- 

 fluous glycerin) be painted with a layer of glycerin jelly ; as 

 soon as this is set a coat of any of the usual cements may be 

 applied. See next chapter. 



Glycerin dissolves carbonate of lime, and is therefore to 

 be rejected in the preparation of calcareous structures that 

 it is wished to preserve. 



430. Extra-refractive Glycerin. The already high index of refrac- 

 tion of glycerin (Price's glycerin, n = 1*46) may be raised by dissolving 

 suitable substances in it. Thus the refractive index of a solution of 

 chloride of cadmium (CdCl 2 ) in glycerin may be 1'504 ; that of a 

 saturated solution of sulphocarbolate of zinc in glycerin may be T501 ; 

 that of a saturated solution of SCHEKJNG'S chloral hydrate (in crusts) in 

 glycerin is 1-510 : that of iodate of zinc in glycerin may be brought up 

 to 1'56. For further details see previous editions, or Journ. Roy. Hie. 

 Soc., ii, 1879, p. 346 ; iii, 1880, p. 1051 ; (N.S.), i, 1881, pp. 943 and 366. 



431. Glycerin and Alcohol Mixtures. These afford one of 

 the best means of bringing delicate objects gradually from 

 weak into strong glycerin. The object is mounted in a drop 

 of the liquid, and left for a few hours or days, the mount not 



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