POL'S BEKLIN BLUE GELATIN MASS. 269 



mixture (A). Stir continually, keeping the temperature at 

 from 20 to 25 E. until the whole of the Prussian blue is 

 precipitated. Finally, heat over a water-bath to about 70 

 E. and filter through flannel. 



480. Fol's Berlin Blue Gelatin Mass (Zeit. f. iviss. Zool., 

 xxxviii, 1883, p. 494). A modification of Thiersch's formula, 

 No. 479. 120 c.c. of a cold saturated solution of sulphate of 

 iron are mixed with 300 c.c. of the warm gelatin solution. 

 In a separate vessel 600 c.c. of the gelatin solution are mixed 

 with 240 c.c. of a saturated solution of oxalic acid, and 

 240 c.c. of a cold saturated solution of red prussiate of potash 

 are added to the mixture. The first mixture is now gradually 

 poured into the second, with vigorous shaking, the whole is 

 warmed for a quarter of an hour over a boiling water-bath, 

 the mass is allowed to set, is pressed out into strings through 

 tulle or netting, as described for the carmine mass, supra, 

 473, and the strings are washed and spread out to dry on 

 the prepared paper. (It is necessary to dry the strings 

 without remelting in this case, because the mass does not 

 readily melt without the addition of oxalic acid.) In order 

 to prepare the mass for injection, the strings are put to swell 

 up in cold water, and then warmed with the addition of 

 enough oxalic acid to allow of complete solution. 



481. Hoyer's Soluble Berlin Blue Gelatin Mass (Arch. f. mik. 

 Anat., 1876, p. 649). The filtered and not too much washed 

 precipitate of soluble Berlin blue is brought in a little water 

 on to a Graham's dialyser, and the external water changed 

 until the solution begins to pass through the parchment. 

 Dilute the solution and filter through filter-paper, an opera- 

 tion which becomes easy after dialysis. The solution may be 

 injected pure (for lymphatics, for instance) or may be com- 

 bined with gelatin. To do this, warm the solution almost to 

 boiling-point, and add gradually a warm, thin solution of 

 gelatin until coagulation begins to set in. Strain through 

 wetted flannel. 



Gelatin Masses of other Colours. 



482. Robin's Cadmium Gelatin Mass (see 463) . 



483. Thier sen's Lead Chromate Gelatin Mass (Arch. f. mik. 

 Anat., 1865, p. 149). 



