230 CEMENTS AND VARNISHES. 



melt in the usual way, stir in 3 drops of creasote. It is used 

 warm. 



When the ring of gelatin has become quite set and dry, it may be 

 painted over with a solution of bichromate of potash made by 

 dissolving 10 grs. of the salt in an ounce of water. This should be 

 done in daylight, in order to render the gelatin insoluble. The 

 cover may then be finished with BELL'S cement. This process is 

 particularly adapted for glycerin mounts. 



461. The Paper Cell Method. By means of two punches I cut 

 out rings of paper of about a millimetre in breadth, and of about a 

 millimetre smaller in diameter than the cover-glass. Moisten the 

 paper ring with mounting fluid, and centre it on the slide. Fill the 

 cell thus formed with mounting fluid ; arrange the object in it ; 

 put the cover on ; fill the annular space between the. paper and the 

 margin of the cover with glycerin jelly (a turn-table may be useful 

 for this) ; and as soon as the gelatin has set turn a ring of gold-size 

 on it, and when that is quite dry, varnish with BELL'S cement. 



For greater safety, the gelatin may be treated with bichromate, 

 according to MARSH'S plan, last . 



462. ROUSSELET'S Method for Aqueous Mounts (op. cit., 458). 

 Close the mount with a ring of a mixture of 2 parts of a solution of 

 damar in benzol and 1 part gold-size. When dry, put on three or 

 four thin coats of pure gold-size at intervals of twenty-four hours, 

 and finish with a ring of WARD'S brown cement. 



463. MILLER'S Caoutchouc Cement. Composition unknown. May 

 be obtained from the opticians. A very tenacious and quickly 

 drying cement. It may be diluted by a mixture of equal parts of 

 chloroform and strong alcohol (see ROUSSELET, Journ. Quek. Club, 

 v, ii, 1895, p. 8). 



464. Asphalt Varnish (Bitume de Judee). Unquestionably one of 

 the best of these media, either as a cement or a varnish, provided it 

 be procured of good quality. It can be procured from the opticians. 



465. Brunswick Black. See ear^y editions, or BEALE, How to 

 Work, etc., p. 49. 



466. Gold-Size. Best obtained from the opticians. It is soluble 

 in oil of turpentine. A good cement, when of good quality, and very 

 useful for turning cells. 



467. Turpentine, Venice Turpentine (CSOKOR, Arch. mik. Anat., 

 xxi, 1882, p. 353 ; PARKER, Amer. Mon. MiL Journ., ii, 1881, 



