BY DR. KLEIN. 109 



permanently. Those which are in liquids, such as glycerin, 

 acetate of potash, bichromate of potash, etc., must be sur- 

 rounded with cement, in order to fix the cover-glass. For 

 those which are in glycerin jelly, Canada balsam (neither of 

 which, however, are to be recommended), or Dammar vnrnish, 

 that is not necessary. Various kinds of varnish are used for the 

 purpose, such as Frankfort lac, asphalt, etc. I use always 

 Dammar varnish. A streak of the varnish is placed on the i-dirc 

 of the cover-glass and carried all round it, with the aid of a 

 glass rod drawn to a point, or a brush, care being taken that it 

 extends only a very little over the cover-glass. Before apply- 

 ing the varnish, the excess of liquid must be carefully removed 

 with blotting-paper from the edge of the cover-glass. I dis- 

 pense with the instrument frequently used for mounting, for the 

 following reasons : If the cover-glass is already fixed, as, e. g., 

 in Canada balsam or Dammar preparations, any additional 

 mounting is unnecessary. If it is not fixed, z. e., when the 

 medium in w r hich the preparation is contained is liquid, there 

 is much greater risk of displacement with the machine than 

 without it. It should always be borne in mind that the pre- 

 servation of the preparation is of more importance than the 

 outside setting. The other kinds of varnish may be used in- 

 stead of labels, for writing on the glass the name of the pre- 

 paration. If it is desired to preserve a preparation already 

 covered in water and solution of osmic acid, or bichromate of 

 potash, etc., without removing the cover, so as to avoid risk 

 of displacement, the best way is to irrigate it with glycerin or 

 acetate of potash, until the one liquid is replaced by the other. 

 The excess of liquid must then be removed with blotting- 

 paper, and the cover-glass surrounded with Dammar varnish. 

 If, by inadvertence, the upper surface of that part of the cover- 

 glass which is above the preparation has been smeared with 

 glycerin or Dammar varnish, and it is desired not to remount 

 it, the only way is to wait until the setting is dry. The spot 

 can then be removed with a camel-hair pencil soaked in water 

 if it be glycerin, or in turpentine and afterwards in alcohol if 

 it be Dammar. 



