124 PREPARATION AND MOUNTING 
are often made; perhaps each of them good for certain 
objects. 
GLYCERINE.—Some affirm this to be one of the best pre- 
servative liquids, especially for vegetable objects; but others 
think that if is much better when diluted with two parts of 
camphor-water, prepared as above.* Mr. A. H. Verrill, of 
Yale College, U.S., says glycerine preserves the natural 
colours of marine animals; and the only precaution to be 
takeh is to use very heavy glycerine, and to keep up the 
strength by transferring the specimens to new as soon as 
they have given out water enough to weaken it much, re- 
peating the transfer till all the water is removed before 
finally mounting on the slide. 
GLYCERINE AND Gum.—This is also believed to be a very 
good liquid for vegetable tissues, and is thus prepared :— 
Pure gum-arabic... 1 oz. 
Glycerine 5... eters es 
Water (distilled)... 1 
Arsenious acid ... 14 grain. 
Dissolve the arsenious acid in the cold water, then the gum, 
add the glycerine, and mix without bubbles. 
Dr. Carpenter states that the proportions used ultimately 
by the late Mr. Farrants are :— 
Picked gum-arabic ... 4 parts by weight, 
Distilled water (cold).. 4 ,, = 
Glycerine. :.. -¢<>/\aeante eee 99 
Thus he now omits the arsenious acid, but places in the 
solution (which should be kept in a bottle with glass stop- 
* Dr. Carpenter says :—‘‘Glycerine has a solvent power for carbo- 
nate of lime;and should not be employed when the object contains 
any calcareous structure. In ignorance of this fact, the author (Dr. 
C.) employed glycerine to preserve a number of remarkably fine speci- 
mens of the pentacrinoid larva of the Comatula, whose colours he was 
anxious to retain; and was extremely vexed to find, when about to 
mount them, that their calcareous skeletons had so entirely disap- 
peared, that the specimens were completely ruined.” 
