STAINING FLUIDS. 231 



it the requisite tint is always better stained than one 

 which has been a much shorter time, because the sur- 

 face becomes stained before the colour has reached the 

 deeper parts. The sections, for the same reason, should 

 be as thin as possible, as they take the stain more per- 

 fectly, and then the deeper portions are seen under the 

 microscope as distinctly as the more superficial. Pro- 

 vided the staining is perfect and sufficient to show 

 all details, the paler it is the better, as it requires 

 less light, and is less likely to fatigue the eye. The 

 tints to be preferred are those that convey a cool and 

 pleasant sensation to the eye. Intense reds and yellows 

 are not nearly so pleasant as lilacs and pale blues. 

 Stains which impart only a body-colour are of no value 

 in differentiating structure. Distilled water should 

 always be used for washing and all staining purposes. 

 A five per cent, neutral aqueous solution of molybdate 

 of ammonia produces a cool blue-grey stain in 24 hours. 

 Eosin is a selective body-stain, which may be used 

 either before or after the sections have been coloured 

 with logwood. One part of eosin dissolved in a 1,000 

 parts of water is quite strong enough. But there 

 is no more useful selective stain, or one more plea- 

 Bant to work with, in Mr. Grroves's opinion, than log- 

 wood. 



Kleinenburg's solution of logwood, modified by 

 Oolding Bird, is prepared as follows : 



1. Make saturated solutions of alum and calcium 

 chloride, in proof spirit. 2. Mix in the proportions of 

 eight of the former to one of the latter. 3. Pound a 

 small piece of ext. hcematoxyli (the older the better) ; 

 add it to the mixed solution, and agitate. After it 

 has been allowed to stand two days, filter for use. 

 A watch-glass should be filled with water, and a few 

 drops of the mixed solutions added, till the fluid 

 acquires a mauve tint. Into this the sections hould 

 be placed, and allowed to remain for twenty-four 

 hours or more. 



Another stain. S chafer's acid logwood solution 

 is especially useful for certain structures, as ten- 

 don, cells, &c. It is thus prepared : A one per cent. 



