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 it is much better when diluted with two parts of 

 camphor-water, prepared as above.* Mr. A. E. Verrill, of 

 Yale College, U.S., says glycerine preserves the natural 

 colours of marine animals ; and the only precaution to be 

 taken 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 1 



Water (distilled)... 1 



Arsenious acid ... 1^ 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 2 



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." 



