THE MICROTOMIST 'S VADE*MECUM

vigorous shaking. (If it be desired to have an extremely
fine-grained mass, both the solutions should be diluted with
three or four volumes of water.) The mass is pressed out
into strings as before, and the strings are stirred up, in clear
daylight, with the following mixture: 14 litres of cold saturated
solution of potassic oxalate to 500 c.c. of cold saturated solution
of sulphate of iron. As soon as the whole mass is thoroughly
black the operation is at an end. The stringsare then washed
for several hours, remelted, and poured on to the prepared an
paper.
This injection appears dark sepia-brown by transmitted
light. If a grey-black hue be preferred, 240 grammes of           0l I
bromide of potassium should be substituted for the sodium
chloride in the first solution.
Fol warns against the employment of anilin colours for
these injection-masses. They diffuse outiduring injection, or,
if not, during the subsequent treatment of the preparations.
Chrome colours are not applicable to dry masses, as treatment a
with chromic compounds causes the gelatin sooner or later to     Do Id
become insoluble.                                                aded
415. Glue Cold Injection-mass (Logwood) (Joseph's for.          dio
mula ).-" Glue liquid when cold, coloured with the violet          a
extract of logwood reduced with alum."        This mass has
similar properties to the white-of-egg mass, No. 416.           Inik
416. White-of-Egg Injection-mass (Carmine) (Joseph's for-      Ug
mula 2).-" Filtered white of egg, diluted with 1 to 5 per cent.  andpal
of carmine solution.   .  . . This mass remains liquid when      does n
cold; it coagulates when immersed in dilute nitric acid,         nRema
chromic or osmic acids, remains transparent, and is sufficiently  Ratial
indifferent to reagents."
For Invertebrates.                                             n
1 ' Ber. naturw. sect. Schles. Ges.,' 1879, pp. 36-40. ' Journ. Roy. Mic.
Soc.' (N.S.), ii (1882), p. 274.
2 Ibid.

272