262 CHAPTER XXI. 



until the curdy precipitate that forms at first lias dis- 

 appeared. Filter through new flannel and keep at 40 C. 

 until injected. 



495. BRUCKE'S Soluble Berlin Blue (Arch. mik. Anat., 1865, p. 87). 

 Make a solution of ferrocyanide of potassium containing 217 grms. 

 of the salt to 1 litre of water, and one of 1 part commercial chloride of 

 iron in 10 parts water. Take equal volumes of each, and add to each of 

 them twice its volume of a cold saturated solution of sulphate of soda. 

 Pour the chloride solution into the ferrocyanide solution, stirring con- 

 tinually. Wash the precipitate on a filter until soluble, dry it, press 

 between blotting paper in a press, break the mass in pieces, and dry 

 in the air. 



The concentrated solution of the colouring matter is to be gelatinised 

 with just so much gelatin that the mass forms a jelly when cold. For 

 another method, see previous editions. 



496. Other Blue Gelatin Masses. HOYER'S, Arch. mik. Anat., 

 1876, p. 649; GUIGNET'S, Journ. de Microgr., 1889, p. 94; Joum. Roy. 

 Hie. Soc., 1889, p. 463 ; THIERSCH'S, Arch. mik. Anat., i, 1865, p. 148 ; 

 FOL'S, Zeit. wiss. ZooL, xxxviii, 1883, p. 494 ; and previous editions. 



Other Colours. 



497. HOYEK'S Silver Nitrate Yellow Gelatin Mass (Biol. Ccn- 

 tralll., ii, 1882, pp. 19, 22). A concentrated solution of 

 gelatin is mixed with an equal volume of a 4 per cent, 

 solution of nitrate of silver and warmed. To this is added a 

 very small quantity of an aqueous solution of pyrogallic 

 acid, which reduces the silver in a few seconds ; chloral and 

 glycerin are added as directed 489. 



This mass is yellow in the capillaries and brown in the 

 larger vessels. 



498. Other Colours. HOYER'S Green (Biol. Centralb., ii, 1882, p. 

 19). Made by mixing a blue mass and a yellow mass. THIERSCH'S 

 Green (Arch. mik. Anat., 1865, p. 149). ROBIN'S SCHEELE'S Green 

 (ROBIN, Traits, p. 37). HARTJNG'S White (see FREY, Le Microscope, p. 

 190). FREY'S White (ibid.). TEICHMANN'S White (ibid., p. 191). FOL'S 

 Brown (Zeit. wiss. ZooL, xxxviii, 1883, p. 494). MILLER'S Purple (see 

 Amer. Mon. Mic. Journ., 1888, p. 50 ; Journ. Roy. Mic. Soc., 1888, p. 518). 

 FOL'S Lead Chromate (Lehrb., p. 15). ROBIN'S Cadmium (his Traite, 

 p. 36). THIERSCH'S Lead Chromate (Arch. mik. Anat., 1865, p. 149). 

 HOYER'S Lead Chromate (Hid., 1867, p. 136); or, for any of these, see 

 early editions. 



