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, &e. 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 tlrs decomposition, 



