STAINING FLUIDS. 227 



To produce a third stain, Schwarz proposed picric 

 acid in combination. A mixture of picro-carmine, he 

 tells us, is a preferable stain for the unstriped muscle 

 of the intestines, &c. Ranvier also employs a picro- 

 carminate ; he discovered that a good green stain could 

 be obtained by dissolving picric acid in glycerine, dilut- 

 ing it with a decoction of logwood, and adding a small 

 quantity of a solution of chromate of potash in the 

 proportion of 1 part to 1,000. The solutions must be 

 mixed together just before they are wanted for use, as 

 they rapidly spoil. 



Dr. W. Stirling 1 f urnishes a brief but useful account 

 of the methods he has employed with success for some 

 time for double and treble staining. 



Osmic Acid and Picro-carmine. Mix on a glass 

 slide a drop of the blood of newt or frog and a drop of 

 a 1 per cent, aqueous solution of osmic acid, and allow 

 the slide to stand by. This will fix the corpuscles with- 

 out altering their shape. At the end of five minutes 

 remove any excess of acid with blotting-paper, add a 

 drop of a solution of picro-carmine, and a trace of 

 glycerine to prevent evaporation, and set aside for three 

 or four hours to see that no overstaming takes place. 

 At the end of this time the nucleus will be found to 

 be stained red, and the perinuclear part yellow. 



Picric Acid and Picro-carmine. Place a drop of the 

 blood of a frog or newt on a glass slide, and add a drop 

 of a saturated solution of picric acid : put the slide aside 

 and allow it to remain for five minutes ; at the end 

 of that time, when the acid has fixed the corpuscles 

 (that is coagulated their contents), any excess of acid 

 should be removed as before. A drop of a solution of 

 picro-carmine should now be added, and a trace of 

 glycerine, and the preparation set aside for an hour. 

 At the end of that time remove the picro-carmine 

 solution by means of a narrow slip of blotting-paper, 

 and add a drop of Farrant's solution or glycerine and 

 apply glass-cover. The perinuclear part of the cor- 

 puscles will be seen to be highly granular and of a 

 deep orange colour, whilst the nucleus is stained red. 



(1) Journal of Anat. and Physiol., xx. 1881, p. 349. 



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