PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS. 211 



second evaporation permitted; the process being repeated, if necessary, until 

 enough Glycerine is left to fill the cell, which is then to be covered and closed in 

 the usual mode. ! 



h. The Glycerine Jelly prepared after the manner of Mr. Lawrence may be 

 strongly recommended as suitable for a great variety of objects, Animal as well as 

 Vegetable, subject to the cautions already given: " Take any quantity of Nel- 

 son's Gelatine, and let it soak for two or three hours in cold water, pour off the 

 superfluous water, and heat the soaked gelatine until melted. To each fluid 

 ounce of the Gelatine add one drachm of Alcohol, and mix well; then add a fluid 

 drachm of the white of an egg. Mix well while the Gelatine is fluid, but cool. 

 Now boil until the albumen coagulates, and the Gelatine is quite clear. Filter 

 through fine flannel, and to each fluid ounce of the clarified Gelatine add six fluid 

 drachms of Price's pure Glycerine, and mix well. For the six fluid drachms of 

 Glycerine, a mixture of two parts of Glycerine to four^ of Camphor-water may 

 be substituted. 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)." 2 A small quan- 

 tity of Carbolic acid may be added to it with advantage. When used, the jelly 

 must be liquefied by gentle warmth, and it is useful to warm both the slide and 

 the cover-glass previously to mounting This takes the place of what was for- 

 merly known as Deane's Medium, in which honey was used to prevent the har- 

 dening of the gelatine. 



i. For objects which would be injured by the small amount of heat required 

 to liquefy the last-mentioned medium, 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 add- 

 ing 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 proceeding: 

 after it has been completed, the liquid should be strained (if not perfectly free 

 from impurity) through fine cambric 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 crack- 

 ing; it is well suited to preserve delicate Animals as well as Vegetable tissues, 

 and in most cases increases their transparence. 



It often is quite impossible to predicate beforehand what preservative 

 medium will answer best for a particular kind of preparation; and it is 

 consequently desirable, where there is no lack of material, to mount simi- 

 lar objects in two or three different ways, marking on each slide the 

 method employed, and comparing the specimens from time to time, so as 

 to judge the condition of each. 



207. In dealing with the small quantities of fluid media required in 

 mounting Microscopic objects, it is essential for the operator to be pro- 

 vided with the means of transferring very small quantities from the ves- 

 sels containing them to the slide, as well as of taking up from the slide 

 what may be lying superfluous upon it. Where some one fluid, such as 

 Diluted Alcohol or the Carbolic acid solution, is in continual use, it will 

 be found very convenient to keep it in the small Dropping-bottle repre- 

 sented in Fig. 138. The stopper is perforated, and is elongated below into 

 a fine tube, whilst it expands above into a bulbous funnel, the mouth of 

 which is covered with a piece of thin Vulcanized India-rubber tied firmly 

 round its lip. If pressure be made on this cover with the point of the 

 finger, and the end of the tube be immersed in the liquid, in the bottle, 



1 See the Rev. W W. Spicer's " Handy-book to the Collection and Preparation 

 of Freshwater and Marine Algae, etc.," pp. 57-59. "Nothing," says Mr. Spicer, 

 "can exceed the beauty of the preparations of Desmidiacece prepared after Herr 

 Han tzsch's method; the form of the plant and the coloring of the endochrome 

 having undergone no change whatever." 



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

 use, is prepared by Mr. Rimmington, chemist, Bradford, Yorkshire. 



