118 PREPARATION AND MOUNTING 



11. For 



Eed 8 parts of size-solution 



(by weight, to 1 part of vermilion. 



Yellow. . 6 " " 1 " chrome yellow. 



White . . 5 " " 1 " flake-white. 



Blue . . 3 " " 1 " blue-smalt, fine. 



Black ..12 " " 1 " lamp-black. 



Whichever of these colours is made use of 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 a rod. 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 capillaries (the minute vessels 

 connecting the arteries with the veins), the " Micrographic Dic- 

 tionary " recommends the colouring matter to be made by double 

 decomposition. As a professed handbook would be, perhaps, 

 deemed incomplete without some directions as to the mode of 

 getting these colours, I will here make use of those given in that 

 work. For red, however, vermilion, as above stated, may be 

 used ; but it must be carefully examined by reflected light to see 

 whether it be free from all colourless crystals or not. It must 

 first be worked in a mortar, and then the whole thrown into a 

 quantity of water and stirred about ; after leaving it not longer 

 than a quarter of a minute, the larger portions will settle to the 

 bottom, and the liquid being poured off will contain the finer 

 powder. This may then be dried slowly, or added to the size 

 whilst wet in the manner before advised. 



13. Yellow injection. To prepare this, take 



