162 PREPARATION AND MOUNTING 
which are found in rhubarb are wanted, some parts con- 
taining these are chosen and left in a small quantity of 
water until the mass becomes soft, and this is more quickly 
effected when the water is not changed. ‘The mass must be 
then placed upon a glass plate when practicable, or in the 
trough when large, and with the aid of two needles the 
matter may be removed from the spiral vessels, which are 
plainly seen with a comparatively low power; and by con- 
veying these to a clean slip of glass, repeating the process, 
and at last washing well, good specimens may be procured. 
Most of these should be mounted in some of the preservative 
liquids in the manner described in Chapter V. Many, 
however, may be dried on the slide, immersed in turpentine, 
and then mounted in balsam ; but liquid is preferable, as it 
best preserves their natural appearance. Certain kinds of 
vegetables require a different treatment to separate these 
spiral vessels. Asparagus is composed of very hard vegetable 
matter, and some have recommended the stems to be first 
boiled, which will soften them to such a degree that they 
may easily be separated. Dilute acids are also occasionally 
used to effect this; and in some instances to obtain the 
vaphides caustic potash may be employed; but after any of 
these agents have been used, the objects must be thoroughly 
cleansed with water, else the dissecting instruments (and 
perhaps the cell) will be injured by the action of the re- 
maining portion of the softening agent. 
For the dissection of animal tissues it is necessary that 
the instruments be in the best order as to sharpness, &c. ; 
and as the rules to be observed must necessarily be some- 
what alike in many instances, the treatment required by 
some of the objects most frequently mounted will now be 
described. We may here remark that cartilage can be 
best examined by taking sections which will show the ar- 
rangement of the cells very perfectly. This, however, is 
plainly seen in the mouse’s ear without any section being ~ 
necessary. Glycerine, the preservative liquids before men- 
tioned, and. Canada balsam are all used to mount it 
