INJECTION GELATIN MASSES. 305 



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. 



492. THIERSCH'S Prussian Blue Gelatin Mass (Arch. f. mik. 

 Anat., i, 1865, p. 148). 

 Take- 



(1) A solution of 1 part gelatin in 2 parts water. 



(2) A saturated aqueous solution of sulphate of iron. 



(3) A saturated aqueous solution of red prussiate of 



potash. 



(4) A saturated aqueous solution of oxalic acid. 



Now (A) mix 12 c.c. of the iron solution with one ounce of 

 the gelatin solution at the temperature of 25 R. 



Then (B) mix, at the same temperature, 24 c.c. of the prus- 

 siate solution with two ounces of the gelatin solution. 



(c) To the latter mixture add first 24 c.c. of the oxalic acid 

 solution, stir well, and then add the gelatin and iron mixture 

 (A). Stir continually, keeping the temperature at from 20 

 to 25 R., until the whole of the Prussian blue is precipitated. 

 Finally, heat over a water-bath to about 70 R. and filter 

 through flannel. 



493. FOL'S Berlin Blue Gelatin Mass (Ze.it. f. iviss. Zool., xxxviii, 

 1883, p. 494). A modification of THIEHSCH'S formula, last , the mass being 

 made into strings and dried, as with the carmine mass, 486. See pre- 

 vious editions. 



494. Other Blue Gelatin Masses. HOYES'S, Arch. f. mik. Anat., 

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

 Mic. Soc., 1889, p. 463 ; or previous editions of this work. 



495. HOYEE'S Silver Nitrate Yellow Gelatin Mass (Biol. Cen- 

 tralbl., ii, 1882, pp. 19, 22; Journ. Roy. Mic. Soc. [N. S.], iii, 

 1883, p. 142). "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 

 before" (No. 485). 



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