5G4 



METHODS AND FORMULAS 



MS 31.6-MS 32.0 



method: [ground sections of teeth] -^ A, 2-5 days — > wash -^ B, till sufficiently reduced 



— ^ water — > C, 2-3 niins. -^ wash — » balsam, via usual reagents 

 RECOMMENDED FOR: dentine. 



31.6 Holmes 1900 11373, 16:371 



REAGENTS REQUIRED: A. 0.75% silver nitrate; B. 0.2% sodium thiosulfate; C. sat. aq. sol. 



picric acid 

 method: [eggs of Planorbis] -^ A, in direct sunlight, till cells clearly demarcated—* 



rinse —» B, wash ^ wash ^ C, 10 mins. -^ 70% ale, wash ^> balsam, via usual 



reagents 

 RECOMMENDED FOR: demarcation of cell outlines in invertebrate embryos. 



31.6 Roskin 1946 Roskin 1946, 292 



REAGENTS REQUIRED: ,4.2% silvcr nitrate; B. 2% hydroquinone 



method: [specimens fixed in F 0000.1010 Roskin 1946] -^ wash -^ A, 10-18 days, 37°C., 

 in dark — > wash, in dark -^ B, 18-38 hrs., in dark — > wash — * balsam, via usual 

 reagents 

 recommended for: general structure in wholemounts of small fresh-water oligochaetae. 



MS 32 METHODS USING PROTEIN SILVER 



These methods, usually referred to as 

 Bodian Techniques (see MS 32.1 Bodian 

 1936 below) are the only silver methods 

 which give satisfactorj^ staining of nervous 

 structures in paraffin sections mounted on 

 the shde. The original method, and most 

 of the modifications, call for Protargol, a 

 proprietar}^ compound conforming to the 

 specifications for "Protein silver, strong, 

 U. S. P. XL" The restricted availabihty 

 of Protargol has lead the author to specify 

 "silver protein" in the methods which fol- 

 low ; all samples of "silver protein, strong," 

 however, do not give satisfactory results, 

 and some selection may be necessary. Con- 

 fusion is sometimes caused by tlie designa- 

 tions "strong" and "mild" as applied to 

 pharmacopeial preparations since the mild 

 contains about three times as much (19% 

 to 25 So) silver as does the strong (7.5% to 

 8.5%). The strength, or mildness, from the 

 pharmacopeial point of \dew, depends on 

 the quantity of ionic silver which is found 

 in solutions of the compound. A method of 

 preparation from gelatin is given by Mos- 

 kowitz 1950 (20540b, 25:17). 



32.0 Typical Example 



Preparation of a transverse section of 

 the sciatic nerve of a cat to demon- 

 strate axis-cylinders by the method 

 of Davenport, Windle, and Rhines 

 1947 



This method departs from the classic 

 Bodian technique in that metalhc copper 



is not used in combination with silver pro- 

 tein to impregnate the nerves. The method 

 is, however, simple and certain, and is 

 recommended in those cases in wliich ab- 

 solute certainty of impregnation of a.xis- 

 cylinders is required. 



Since the method of fixation is an inte- 

 gral part of this technique, the removal 

 and the fixation of the sciatic nerve will 

 first be described. The fixative recom- 

 mended is a mixture of formamide and 

 paranitrophenol, and is given under the 

 heading F 9000.4000 Davenport, Windle, 

 and Rhines 1947 in Chapter 18. Care must 

 be taken to secure pure formamide, as the 

 commercial grade is worthless for the pur- 

 pose. About 100 milliliters of fixative will 

 be required, and it is prepared by dissolv- 

 ing 5 grams paranitrophenol in 45 milli- 

 Uters of 95% alcohol, and then adding to 

 the mixture 10 grams of formamide. After 

 all these ingredients are mixed, 45 milli- 

 liters of distilled water is added. 



The cat has been selected, rather than 

 the rabbit recommended in other ex- 

 amples, because of the relatively large size 

 of the sciatic nerve. A freshly killed cat 

 should be secured and the skin removed 

 from the lateral side of the upper part of 

 the leg. This exposes the biceps femoris 

 muscle which may be lifted by slipping 

 the handle of the scalpel under it and 

 running the scalpel down from the origin 

 towards the insertion. The aponeurosis at 

 the knee can then be cut, either with a 

 scalpel or scissors, and the muscle laid 



