AS MICROSCOPICAL OBJECTS. 475 



The following reagents, which should be brought to exactly 

 the proper consistency for easy working by the addition of their 

 respective diluents, will be required : Gold- size, caoutchouc 

 cement (Millar's), and Club black. As a mounting medium mix 

 equal parts of whisky and glycerine. This should be carefully 

 filtered, or else allowed to stand for a few days and decanted. 



Place a slip on the turn-table, and run upon it a ring of gold- 

 size | in. in diameter. Take a cell, and, by means of a pair of 

 forceps, drop it on to the ring of gold-size, pressing down to 

 ensure good contact. Prepare a number of these slips, using 

 cells of different depths, and put them aside for a week to dry. 

 Do not forget that as excavated slips are being used, a larger 

 proportion of thin cells will be required, unless very large objects 

 are to be mounted. If any considerable amount of work of this 

 kind is contemplated, some means of judging the relative thickness 

 of cells will be useful — for example, a piece of brass with slots of 

 different widths in it. 



Take the whisky-soaked palpus and place it in one of the 

 deepest cells, fill up with whisky, and place a temporary cover- 

 glass upon it, holding it in position by means of a wire-clip. Now 

 turn the slide about, and observe what happens. If the cell is 

 very deep compared with the thickness of the object, this latter 

 will fall to the side. If somewhat shallower, the object will only 

 reach the margin, or near to the margin, of the now practically 

 invisible excavation in the slip. Try cells of various depths until 

 the one is found which will produce the desired result, which 

 may be to keep the object perfectly still, or else to allow it a 

 certain amount of movement. Minute dissections may be mounted 

 in the excavation without the use of a tin cell at all. 



The proper slip having been found, it is thoroughly cleaned, 

 placed upon the turn-table, and a ring of caoutchouc cement run 

 upon the upper surface only of the tin cell. This is allowed to 

 remain for (say) a quarter of an hour, until it can just be gently 

 touched with the finger without adhering. The cell is then 

 filled to overflowing with the glycerine and spirit mixture, the 

 dissection is introduced and arranged, and a cover-glass put on, 

 and held in position with a weak wire-clip. The whole is now 

 held under a gentle stream of water from a tap, in order to get 

 rid of every trace of the glycerine from the glass. The whole 

 success of the process depends upon this being thoroughly 

 accomplished. 



