OF MICROSCOPIC OBJECTS. 185 
sections very thin. Some few of this kind undergo compara- 
tively little change in drying, so that the section may be 
well washed and floated upon the glass slide in the place 
desired, where it will dry perfectly and adhere to it. It 
must then be moistened with turpentine and mounted in 
Canada balsam like other objects. No great heat should be 
used with these preparations, as it is very liable to injure 
them; and some of the colours seem to suffer a slight con- 
traction when any great degree of warmth is applied. There 
are many objects, however, which must be seen in the mass 
to be understood, and, indeed, lose all their form and beauty 
in drying, such as certain parts of the intestines, &c. These 
must be mounted in fluid, with the precautions noticed at 
length in Chapter V., and for this purpose either Goadby’s 
fluid, the chloride of zinc solution, or spirit diluted with ten 
parts of distilled water, may be employed. It is a good 
thing, when practicable, to mount similar objects on two 
separate slides, using different preservative liquids, and 
taking the precaution of marking each with the kind of 
liquid employed. This not only serves as a guide to what is 
best for certain subjects, but if one is injured, there will 
probably be a good specimen in the other. 
25. It may be here mentioned that many are now mount- 
ing sections of injected substances with the balsam and 
chloroform before mentioned, instead of using balsam alone, 
and consider that the labour is much lessened thereby. 
26. A description of that mode of injection which is most 
generally employed has now been given, but this is not the 
only method of effecting our object. A most ingenious 
process was invented by M. Doyers, requiring no artificial 
warmth, by which many beautiful objects have been pre- 
pared. Make a solution of bichromate of potash, 524 grains 
to a pint of water, and throw this into the vessels to be 
injected; then take 1,000 grains of acetate of lead dissolved 
in half a pint of water, and force this into the same vessels. 
A decomposition now takes place in the vessels, and the 
yellow chromate of lead is formed. In this decomposition, 
