322 MICROSroPTPAL TEPHXIQUE. 



rontrol the various stages of the process by examining the speci- 

 mens from time to time, as well as to check the action of the 

 dyes at the right moment. — B. M./,, No. 1,678, p. 400. 



Method of Finishing Slides.*- The following is the process 

 devised by Dr. Frank L. James {St. Louis Med. a?id Surgical 

 Journal), and now in general use among American Microscopists : 

 Precipitate an aqueous solution of gum arabic by adding alcohol 

 until no further separation occurs. Filter to get rid of the liquid, 

 and wash the precipitate on the filter with alcohol ; collect, dry, 

 and when dry redissolve the material in distilled water, to which 

 about I per cent, of glycerin has been added. To this solution add 

 about 2 per cent, of aluminium sulphate, and stir in sufficient talc, 

 dry kaolin, or some such substance, to make a cement with a good 

 body. 



With this cement spin on your slips a ring of sufficient depth 

 to act as a cell-wall for the mount. After mounting in balsam, or 

 dammar, as soon as the surplus resin is dry, remove it with a knife 

 or other means, and with a little benzol clean the slides around 

 the cover-glass. Replace on the turn-table, and run round the 

 edges a little of the cement, let dry, and then finish with Bruns- 

 wick black, or any other of the oleagenous or resinous cements. 

 The above method only applies to those preparations requiring a 

 cell-wall. The ordinary balsam or dammar mounts, where no 

 cell is necessary, are finished by removal of the surplus balsam, as 

 directed above, and the application of the cement. For this class 

 of mounts the addition of talc, etc., to the arabicin solution is not 

 necessary, as the solution itself on drying leaves an intermediary 

 coating impervious to benzol, chloroform, oil, or alcoholic solutions 

 of the gums, etc., and Brunswick black applied to it will remain 

 firmly adherent for an indefinite time. One precaution only is 

 necessary, and that is to make the intermediary ring around the 

 cover-glass so narrow that the finishing ring of Asphalt or 

 Brunswick black shall overlap it both on the cover-glass and slide. 

 Even a ring of plain gum arabic in aqueous solution will be 

 sufficient to prevent the running in of the asphalte, etc. 



* National Druggist, April, 1 89 1. 



