178 PREPARATION AND MOUNTING 
as Nelson’s or Cox’s: some persons of experience prefer the 
latter. 
10. Colowrs.—The  size-solution above mentioned will 
need some colouring matter to render it visible when in- 
jected into the vessels of an animal, and different colours 
are used when two or more kinds of vessels are so treated, 
in order that each set may be easily distinguished by 
sight. The proportion in which these colours are spi to 
the size-solution may be given as follows :— 
11. For 
BRE 6. show 8 parts of size-solution 
(by weight) to 1 part of vermilion. 
Yellow... 6 BS & 1,4, chrome yellow. 
White 5 Be “ 1 .,  flake-white. 
Blue, ..... 3 e a 1 =, blue-smalt, fine. 
Black ...12 & m 1,4, ~—lampblack. 
Whichever of these colours is used must be levigated in a 
mortar with the addition of a very small quantity of water 
until every lump of colour or foreign matter is reduced to 
the finest state possible, otherwise in the process of injecting 
it will most likely be found that some of the small channels 
have been closed and the progress of the liquid stopped. 
When this fineness of particles is attained, warmth sufficient 
to render the size quite fluid must be used, and the colour 
added gradually, stirring all the time with arod. It may 
be here mentioned that where one colour only is required, 
vermilion is, perhaps, the best; and blue is seldom used 
for opaque objects, as it reflects very little more light than 
black. 
12. When it is wished to fill the caollarea (the minute 
vessels connecting the arteries with the veins), the Micro- 
graphic Dictionary recommends the colouring matter to be 
made by doyble decomposition. As a professed handbook 
would be, perhaps, deemed incomplete without some direc- 
tions as to the mode of getting these colours, I will here 
