1882.J 



MICROSCOPICAL JOURIS^AL. 



231 



thereby. On replacing the water by 

 alcohol — a still less dense fluid — 

 more of the finer air-spaces are pene- 

 trated and the air driven out : there 

 are still, however, some tubes too 

 minute even for alcohol rapidly to 

 enter. So now we pour off the spirit, 

 and add ether instead, which answers 

 a double purpose; — it enters readily 

 the very minutest passages, displacing 

 the contained air, and it also dis- 

 solves the globules of fat left unsa- 

 ponified by the soda-solution. After 

 leaving the ether for fifteen minutes 

 in the corked tube, and shaking it 

 once or twice, we pour it off and add 

 turpentine; and then in ten itiinutes' 

 time our blow-fly's head is ready for 

 mounting in Canada balsam or dam- 

 mar. 



But if so mounted, it will be very 

 difficult to see much of the finer inter- 

 nal structure, since these media ren- 

 der some parts far too transparent; 

 hence some of the glycerin me- 

 dia are preferable. In such cases, 

 after pouring off the ether add 

 alcohol and at the end . of fif- 

 teen minutes replace the alcohol 

 with cold water, and leave for 

 fifteen minutes more. Then the 

 water, may be poured off, and the 

 mounting-fluid, whether glycerin, 

 carbolic acid, gelatine, Goadby's or 

 Thwaites' fluid, may be added. The 

 object, if mounted in any of these, 

 will have a far more natural appear- 

 ance, and show more plainly the finer 

 structures, than if mounted in Canada 

 balsam. The times mentioned above 

 are those it is necessary in most cases 

 to wait, but longer intervals would 

 often be preferable. If we are busy, 

 the tube and its contents may be left 

 at any stage of the proceedings for 

 days, with a certainty that the object 

 will only benefit by the delay; except 

 in the case of the soda-solution. Of 

 course, when the object is transparent 

 enough, a longer stay in that solution 

 would only render it too transparent, 

 and so spoil it. It is not necessary 

 to use distilled water, though it is 

 better to do so; but whatever water 



is used, it should have been just 

 freshly boiled and be used hot. 

 Cold, unboiled water contains a large 

 quantity of air, and if used in that 

 state will certainly impart air to the 

 object instead of helping to extract it. 



The soda or potash-solution is 

 made by adding solid potash or soda 

 to eight times its weight of boiling 

 water. 



The spirit and the ether, which 

 have been used during the process, 

 should be poured off into a separate 

 waste bottle, either to be afterwards 

 redistilled, or for use in some other 

 way : — ether, being highly inflam- 

 mable, should not be brought near a 

 light. The only expenses are for 

 soda, alcohol, ether, and one tube; of 

 the alcohol and ether there is prac- 

 tically very little waste, as a pint of 

 each will prepare some thousands of 

 specimens. 



So far, we have written as if it were 

 only the blow-fly's head that we 

 wished to prepare ; but it is obvious 

 that in the same tube we may have 

 some dozen or more insects, or parts 

 of insects, — only being careful to 

 remember which is which. The same 

 system will answer likewise for plant 

 specimens, such as sections of wood, 

 small seed-vessels, leaves, etc. Only 

 in their case they should first be de- 

 colored by pouring sodic hypo- 

 chlorite into the tube ; then, after well 

 washing with water, the rest of the 

 process may be followed as before, 

 leaving out entirely the use of the 

 soda-solution. The great difference 

 is in the matter of speed, as vegetable 

 preparations can be made far more 

 rapidly than insect ones. It is pos- 

 sible by this method to cut a dozen 

 sections from a living branch, — 

 bleach, stain, and mount them in 

 Canada balsam or glycerin-solution, 

 — and finally, ring and label them, all 

 within the hour. 



Should some of the preparations — 

 our Blow-flly's head, for instance — 

 become too colorless and transpar- 

 ent, all we have to do is to stain such 

 by the addition of a few drops of an 



