124 PREPARATION AND MOUNTING 



lated so easily; but where the injections are opaque, there is no 

 need to have the sections very thin. Some few of this kind un- 

 dergo comparatively 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 be 

 then moistened with turpentine and mounted in Canada balsam 

 like other objects. No great heat should be used with these pre- 

 parations, as it is very liable to injure them ; and some of the 

 colours seem to suffer a slight contraction 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 intes- 

 tines, &c. These must be mounted in fluid, with the precautions 

 noticed at length in Chapter IV., 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 mounting 

 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 prepared. 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 1000 grains of ace- 

 tate of lead dissolved in half a pint of water, and force this into 

 the same vessels. A decomposition now takes place in the ves- 

 sels, and the yellow chromate of lead is formed. In this decom- 

 position, however, the acetate of potash also is formed, and as this 

 salt has an injurious action upon the cells, Dr. Goadby recom- 

 mends nitrate of lead to be used, which preserves rather than de- 



