HARDWICKE'S SCIENCE-GOSSIP. 



12 I 



THE PREPARATION OF INSECTS FOR MICROSCOPICAL 



EXAMINATION. 



[Continued from p. 103.] 



ND now as to the 

 question of stain- 

 ing. Some have 

 strong objections 

 to staining speci- 

 mens, for they say 

 that it merely makes 

 the object prettier, 

 and that the natural 

 colour is destroyed. 

 These objections 

 are quite sufficiently 

 answered by the 

 consideration that 

 staining does more 

 than beautify an ob- 

 ject, — details visible 

 with difficulty or 

 not at all in an un- 

 stained specimen, 

 are easily seen in 

 one that is properly stained ; and why, after all, should 

 a slide not be made as beautiful as possible ? As for 

 destroying the natural colour, that is generally done 

 in the ordinary process of mounting. I am therefore 

 in favour of staining, if it be properly done. 



The following are the stains which I use : — Dr. 

 Beale's carmine fluid. The recipe for this may be 

 found in so many books, that it is unnecessary to 

 give it again. Aquasous anilin blue. — Dissolve ten 

 grains of anilin blue in one drachm of spirits ; add 

 half an ounce of distilled water, and half an ounce of 

 glycerine, and filter : let the mixture stand for a week 

 or a fortnight, and then pour off the clear fluid for use. 

 Anilin blue in oil of cloves. — Dissolve five grains of 

 anilin blue in half a drachm of absolute alcohol. Mix 

 the solution with an ounce of oil of cloves, and filter it 

 through blotting paper. Magenta fluid.— 1. A few drops 

 of Judson's magenta dye in water, to which a little 

 glycerine has been added. This is chiefly for staining 

 chitine. 2. A very weak solution of the dye in 

 methylated spirit. This is for staining muscles. 

 No. 174. 



Haematoxyline. — Boil some logwood in water until a 

 strong infusion is made ; filter; dissolve a quarter of an 

 ounce of alum in an ounce of water ; mix, say twenty 

 drops of the logwood infusion with about an ounce 

 and a half of distilled water, and add enough of the 

 alum solution to make the fluid a bright purple ; 

 filter, and the stain is ready for use. ' With the 

 exception of anilin blue in oil of cloves, which is 

 rather expensive, all these fluids cost next to nothing. 

 No precise directions can be given for staining, 

 because the process requires to be varied a little for 

 almost every object, but a little information as to the 

 various properties of the different fluids will be useful. 

 Carmine fluid does not stain chitine in the least, but 

 it is excellent for internal organs and muscular tissue. 

 The only objection to it is that it will not keep more 

 than a month. A solution of hrematoxyline, of about 

 one-fourth of the strength of the recipe given above, 

 answers every purpose of carmine fluid. It is not 

 such a pretty colour, but it will keep very much 

 longer. Muscular tissue needs about half an hour's 

 immersion in this fluid to stain it a nice colour. 

 Haamatoxyline, according to the recipe, stains chitine 

 very nicely. The time required to colour the object 

 properly varies from half a day to forty-eight hours. 



Specimens stained with carmine or hsematoxyline 

 may be mounted in either glycerine or balsam, but 

 those stained by any of the other fluids can be mounted 

 in balsam only. Aqueous anilin blue is a very useful 

 stain. It will stain chitine fairly well, but not when 

 it is very hard, as in the barbs of a wasp's sting. It is 

 good for such things as mites, flies' mouths, and 

 especially for Crustacea, such as entomostraca, wood- 

 lice, &c. Magenta will stain anything, but it has a 

 special affinity for chitine. It is very soluble in 

 alcohol, and specimens stained with it must be 

 hurried through the alcohol into oil of cloves in a k\v 

 minutes, or all the colour will be washed out. By 

 taking advantage of its special affinity for hard 

 chitine, a very beautiful and instructive double stain- 

 ing may be effected in this way. Use a watch glass 

 for soaking the specimens in absolute alcohol : pour 



G 



