GELATINOUS AND ALBUMINOUS INJECTION-MASSES 267
* bichromate solution. Then warm almost to boiling point, and
add gradually the (warmed) sugar of lead solution. Allow
f the mass to cool down to body temperature and inject at
once. Another mode of preparation is as follows: Mix the
sugar of lead solution with part of the gelatin solution, mix
)  the bichromate solution with the remaining gelatin solution,
heat the latter mixture, and pour into it the former mixture
(gradually), stirring continually.
If the solutions are mixed at a low temperature a lumpy
granular precipitate is formed. Further, when solution of
sugar of lead is added to a hot solution of bichromate of
1  potash, a rich orange red precipitate is obtained; whilst if the
solutions be mixed cold, the precipitate is bright yellow.
r If the solutions of the two salts be kept ready prepared,
the injection-mass may be mixed in less than a quarter of an
hour. Its advantages are, that on account of the extremely
fine state of division of the precipitate the mass is almost
transparent, and runs so freely that even lymphatics may be
l   perfectly injected with it, whilst its intensity of colour makes
the vessels much more distinct than the very pale mass of
Thiersch (No. 402).      It is also easier to manage than
Thiersch's mass, as it does not solidify so quickly. It shows
F* well in the vessels by reflected, as well as by transmitted,
light.
11)    405. Gelatin Injection-mass (Nitrate of Silver) (Banvier's
formula ').-Concentrated solution of gelatin, 2, 3, or 4 parts;
1 per cent. nitrate of silver solution, 1 part.
406. Gelatin Injection-mass (Yellow.-Silver Nitrate)
tO of  (Hoyer's formula )    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
1 ' Trait6,' p. 123.
2 , Biol. Centralbl.,' ii (1882), pp. 19, 22. ' Journ. Roy. Mic. Soc.'
(N.S.), iii (1883), p. 142.