222 PRESERVATIVE MEDIA. 



of two parts of Glycerine to four of Camphor-water may be sub- 

 stituted. The objects intended to be mounted in this medium are 

 best prepared by being immersed for some time in a mixture of 

 one part of Glycerine with one part of diluted Alcohol (1 of alcohol 

 to 6 of water)."* For many objects which would be injured by 

 the small amount of heat required to melt either of the two 

 last -mentioned media, the Glycerine and Gum medium of Mr. 

 Farrants will be found very useful. This is made by dissolving 

 4 parts (by weight) of picked Gum Arabic in 4 parts of cold 

 Distilled Water, and then adding 2 parts of Glycerine. The 

 solution must be made without the aid of heat, the mixture 

 being occasionally stirred, but not shaken, whilst it is pro- 

 ceeding : after it has been completed, the liquid should be 

 strained (if not perfectly free from impurity) through fine cam- 

 bric previously well washed out by a current of clean cold water ; 

 and it should be kept in a bottle closed with a glass stopper 

 or cap (not with cork), containing a small piece of Camphor. The 

 great advantage of this medium is that it can be used cold, and 

 yet soon viscifies without cracking ; it is well suited to preserve 

 delicate Animal as well as Vegetable tissues, and in most cases 

 increases their transparence. For the preservation of Micro- 

 scopic preparations of Animal structures, a mixture of one part of 

 Alcohol and five of Water will generally answer very well, save in 

 regard to the removal of their colours ; if it should have the effect 

 of rendering them opaque, this will be neutralized by the addition 

 of a minute quantity of Soda. A mixture of Glycerine and Cam- 

 phor-water in about the same proportion answers very well for 

 many objects, especially when it is desired to increase their trans- 

 parence, and it is more favourable than Diluted Alcohol to the 

 preservation of colour ; but in using this menstruum it must be 

 borne in mind that Glycerine has a solvent power for Carbonate of 

 Lime, and should not be employed when the object contains any 

 Calcareous structure. + For preserving very soft and delicate 

 marine Animals, such as the smaller Medusa? and Annelida, the 

 Author has found a mixture of about one-tenth of Alcohol and the 

 same of Glycerine, with Sea-water, the most effectual in pre- 

 serving their natural appearance ; and the same mixture, with 

 increased proportions of alcohol and glycerine, answers very well 

 for larger objects. For Zoophytes, and many other marine objects, 



* A very pure Glycerine jelly, of which the Author has made consider- 

 able use, is prepared by Mr. Riinniington, chemist, Bradford, Yorkshire. 



t In ignorance of this fact, the Author employed Glycerine to preserve 

 a number of remarkably fine specimens of the Pentacrinoid larva of the 

 Comatula (Plate xxi.1, whose colours he was anxious to retain ; and was 

 extremely vexed to find, when about to mount them, that their Calca- 

 reous skeletons had so entirely disappeared that the specimens were 

 completely ruined. This result might pei-haps be prevented, if the Gly- 

 cerine were previously saturated with Carbonate of Lime, by keeping it 

 for some time in a bottle with chips of Marble. 



