MS 34.0 



METAL STAINS 



599 



method: [pieces of fresh muscle infested with Trichiiicna] -^ A, 10 mins. — > wash — » B, 

 till muscle {not worms) decolorized -^ wash — » C, till worms tiro iodine free -^ wash 

 — * D, till muscle colorless—* wash—* balsam, via usual reagents 



RECOMMENDED FOR: Trichlnella in muscles. 



MS 34 METHODS USING SILVER IN COMBINATION WITH OTHER 



METALS 



34.0 Typical Examples 



Demonstration of the Purkinjc 



cells in the cerebellar cortex by 



the method of Golgi 1875 



This method is not one which can be 

 recommended to anybody who desires 

 hurriedly to produce a slide. It is an ex- 

 perimental method given here for those 

 who have a genuine interest in the pro- 

 duction of beautiful slides. The two other 

 Golgi processes given under MS 34.21 be- 

 low are considerably quicker but they are 

 less certain and give less opportunity for 

 experiment. By the method about to be 

 described it is possible, with patience, to 

 secure a better slide than can be obtained 

 by any other method. 



The first step is to make up at least 100 

 milliliters of Miiller's 1859 dichromate- 

 sulfate (Chapter 18 F 7000.0000 Miiller 

 1859) and weigh out, into each of three 

 small tubes or capsules, one gram of finely 

 powdered potassium dichromate. Next 

 prepare about 250 milliliters of a 0.75% 

 solution of silver nitrate and secure two 

 chemically cleaned lOO-milhUter stop- 

 pered bottles and a chemically clean crys- 

 talhzing dish of about 30 milliliter 

 capacity. 



Kill a rabbit, tie it face down on a 

 board, skin the head, and remove the 

 parietal and frontal bones with bone for- 

 ceps. The cerebellum should then be 

 washed free of extravasated blood with 

 normal saline or triple-distilled water, and 

 blocks of the cerebellar cortex removed 

 with the broken edge of a coverslip or with 

 a stainless steel knife. (Many failures in 

 using this technique are due to cutting 

 blocks of material with an ordinary steel 

 scalpel.) The blocks should measure about 

 }i mm. to % mm. cube. At least 30 are 

 required for experimental purposes. These 

 blocks are now placed in the stoppered 



bottle of Miiller's fluid (F 7000.0000 Mul- 

 ler 1859). It is desirable to place a half- 

 inch layer of fat-free cotton or fine glass 

 fiber on the bottom of the bottle to pre- 

 vent the pieces of material from pressing 

 against the glass. The pieces should be left 

 in Miiller's fluid for five days, and the 

 bottle gently shaken daily to avoid ex- 

 hausting the fixative in the vicinity of the 

 pieces. On the fifth day add one of the one- 

 gram bottles or capsules of dried potas- 

 sium dichromate, tip the bottle up and 

 down until the chemical is thoroughly dis- 

 solved, and then let it stand five days 

 longer. On the tenth day add another 

 gram of potassium dichromate and let it 

 stand five days longer. On the fifteenth 

 day remove two or three of the blocks and 

 place them without washing in about 25 

 milliliters of 0.75 silver nitrate in the 

 crystalizing dish. Add one gram of potas- 

 sium dichromate to the fluid which holds 

 the remaining blocks, dissolve as before, 

 and leave for two days more. 



Returning now to the two blocks which, 

 for experimental purposes, have been put 

 in the silver solution: these should be 

 agitated rapidly to keep the precipitate 

 from adhering to the surface as it forms. 

 The silver nitrate after a few minutes 

 should be poured off and replaced with 

 fresh solution. This process of pouring off 

 the contaminated solution and adding 

 fresh is continued until the pieces rest at 

 the bottom and no longer exude streams 

 of a silver chromate precipitate. After 

 they have remained in this satisfactory 

 condition for about ten minutes they are 

 removed to a stoppered bottle containing 

 100 milliliters of fresh 0.75 % silver nitrate. 

 There they may remain indefinitely. They 

 should be marked in some manner, pref- 

 erably by notching the edge, so that they 

 can be identified. 



Two more blocks should be removed 

 from the dichromate solution at intervals 



