STAINS, ETC. 



acid ; in other respects the formulae are alike. 

 Iodin. A good and rapid fixing agent for delicate 

 tissues. Lugol's solution may be used, of which the 

 formula is as follows : Iodin 4 parts, potassium 

 iodid 6 parts, water loo parts. Ranvier recommends 

 a saturated solution of iodin in a saturated aqueous 

 solution of potassium iodid, filtered, and diluted to a 

 brown-sherry color. Johnson's {Lindsay) Fluid. 

 Potassium bichromate, 2.5 per cent., 65 parts; 2 per 

 cent, osmic acid 15 parts, 2 per cent, platinum 

 chlorid 15 parts, acetic or formic acid 5 parts. Ten 

 parts of a 5 per cent, solution of uranium nitrate may 

 be added ; this will prevent the tendency of the osmic 

 acid to blacken and will give a delicate chestnut- brc. n 

 tint. Klein's Fluid. This should be freshly pre- 

 pared and kept in the dark. It is made by mixing 2 

 parts of 6 per cent, chromic acid with 1 part of methyl- 

 ated spirit. For hardening the intestine Klein recom- 

 mends a 5 per cent, solution of neutral ammonium chro- 

 mate. Kleinenberg's Fluid. Picro-sulpliuric Acid. 

 This reagent is especially adapted for fixing embryonic 

 tissue and soft pathologic structures, as sarcoma and 

 myxoma. It is prepared as follows: to loo c.c. of a 

 saturated aqueous solution of picric acid add 2 c.c of 

 strong sulphuric acid ; after an hour filter, and to the 

 filtrate add 300 c.c. of distilled water. A few hours 

 to several days are required for fixation. Wash in 

 warm alcohol to remove the acid. Kolossow's 

 Fluid. Recommended for its great penetrating 

 power. It consists of a 0.5 per cent, solution of 

 osmium in a 2 or 3 per cent, solution of uranium 

 nitrate or acetate. Kultschitzky's Fluid fixes tis- 

 sues without causing the precipitation of the albu- 

 minoids, so likely to occur in solutions containing 

 chromic acid. It is prepared by adding in excess 

 finely powdered potassium bichromate and copper sul- 

 phate to 50 per cent, alcohol, and placing in the dark 

 for 24 hours. At the moment of using, add a few 

 drops of acetic acid, 5 or 6 to 100 c.c. Fix objects 

 for 12 to 24 hours in the dark, then treat with strong 

 alcohol, and they are ready for sectioning. Lang's 

 Sublimate Solution. Used for fixing Planar ia. Its 

 composition is as follows : mercuric chlorid 5 grams, 



' sodium chlorid 6 grams, acetic acid 5 c.c, water, 

 loo c.c. The Planaria are placed on their backs and 

 the fluid poured over them. After half an hour they 

 are placed in 70 per cent., then in 90 per cent., and 

 then in absolute alcohol. They are sufficiently 

 hardened in two days. Lemon-juice. Recom- 

 mended by Van Gehucten as a fixative for nuclei. It 

 should be fresh and filtered. Fix for five minutes, and 



; wash out in water. Mercuric Chlorid. See Cor- 

 rosive Sublimate. Merkel's Fluid. A delicate 

 reagent, used for hardening fish ova, and consisting of 

 equal volumes of 1. 4 percent, chromic-acid and 1. 4 

 per cent, platinum-chlorid solutions. Several hours 

 or days may be required for penetration. Prick the 

 ova and wash in alcohol of 50 to 70 per cent. A few 

 i' immersion in this fluid will, it is claimed, 



effectually prevent blackening of objects fixed in osmic 

 acid. Muller's Fluid. This agent is very exten- 

 sively used, as it penetrates well and hardens evenly. 

 It has the following composition : potassium bichro- 

 mate 2.5 parts, sodium sulphate I part, water loo 

 parts. The addition of a little camphor, chloral, 

 thymol, or naphthalene will prevent the formation of 

 mold. The time required for hardening depends on 

 the size of the object. This fluid diluted to 0.2 per 

 cent, is used as a macerating agent. Osmic Acid. 

 An aqueous solution is used in strengths varying from 

 3 -05 to 2 per cent. The time required for fixing de- 

 pends on the object and the strength of the solution, 



1383 FIXING AND HARDENING FLUIDS 



and varies from a few seconds for Infusoria in a 0.5 per 

 cent, solution to 24 hours for tactile corpuscles in a I 

 per cent, solution. The osmium must be thoroughly 

 removed by washing in water, as any remaining in the 

 tissue in time over-colors it. Solutions of osmic acid 

 must be protected from the light at all times. Fatty 

 tissue should have the fat dissolved out by alcohol be- 

 fore immersion in osmic-acid solutions, or it may after- 

 ward be decolorized by turpentine. For delicate 

 membranes osmic acid may also be employed in the 

 form of vapor. As a macerating agent for the cortex 

 cerebri (Rindrleisch), a o. 1 per cent, solution is used, 

 and may be followed by dissociation in glycerin. A 



1 or 2 per cent, solution is the best fixing agent for 

 blood. Palladium Chlorid. Recommended by 

 Cattaneo as the best fixative for Infusoria. It is pre- 

 pared by dissolving 10 grams in one liter of water 

 containing 5 or 6 drops of hydrochloric acid. One or 



2 minutes' immersion will suffice for the fixation of 

 small objects. It is an impregnation reagent, and 

 colors certain tissue-elements in various tones of brown. 

 According to Schultze, it has a special faculty for 

 penetrating tissues rich in connective tissue, and gives 

 a better consistence than chromic acid or Muller's 

 fluid. Paladiuo's Palladium Chlorid. Used to de- 

 monstrate the axis-cylinders in peripheral nerves. 

 After hardening in potassium - bichromate solution 

 place the tissue in a o. I per cent, solution of palladium 

 chlorid, to which a little hydrochloric acid has been 

 added ; in 2 or 3 days transfer to a 4 per cent, solution 

 of potassium iodid for I to 2 hours. Dehydrate and 

 embed in paraffin. Perenyi's Fluid. An important 

 embryologic reagent. It produces perfect fixation of 

 segmentation -spheres and nuclei, and has the advantage 

 that fuchsin, eosin, picrocarmin, and other stains may 

 be dissolved in it. It is composed of 10 per cent, nitric 

 acid 4 parts, absolute alcohol and 0.5 per cent, 

 chromic acid each 3 parts. Picro-nitric Acid. 

 Mayer's for tnula. Water loo c.c, nitric acid (25 

 per cent. N 2 5 ) 5 c.c, and as much picric acid as will 

 dissolve in the mixture. The properties of this fluid 

 are similar to those of picro-sulphuric acid, and it has 

 the advantage of not crystallizing lime-salts in tissues 

 containing them. Eight c.c. of 25 per cent, hydro- 

 chloric acid may be substituted for the nitric acid, the 

 mixture possessing the same properties and being 

 known as picro-hydrochloric acid. Picric Acid. A 

 fixing agent of great penetration, and, therefore, espe- 

 cially suitable for the preparation of chitinous structures. 

 A saturated solution is employed. The time required 

 for fixation varies from a minute to a day, and depends 

 on the size of the object. Wash out in alcohol and stain 

 in alcoholic solutions. Platinum Chlorid (Rabl). 

 Objects are placed in an aqueous solution, I : 300, for 

 24 hours, then washed with water and hardened in 

 alcohol. Safranin or Delafield's hematoxylin may be 

 used to stain. This reagent is valuable in the study 

 of karyokinesis. It renders Pfitzner's granules and 

 the longitudinal division of the elements plainly 

 visible. Potassium Permanganate (Du Plessis). 

 Useful for the study of isolated and very contractile 

 cells, as spermatozoa. It is said to kill more rapidly 

 than any other agent, 2 per cent, osmic acid not 

 excepted. A saturated aqueous solution is used. 

 It is also used for washing out over-staining with 

 carmin, and in I per cent, solution as a mordant 

 for anilin dyes (Henneguy), and for reducing silver 

 impregnations. Rabl's Fluid. Especially useful 

 for the study of mitosis and nuclei generally. It 

 must be freshly prepared at the moment of using, 

 and consists of 200 c.c. of 0.33 per cent, chromic 

 acid and 4 or 5 drops of formic acid. Fix for 1 2 to 24 



