The Microscope. 365 



ELEMENTARY DEPARTMENT. 



TENTH LESSON. 



" CLEANLINESS IS AKIN TO GODLINESS." 



"lY/TOUNTING IN A CELL. Before entering on a description 

 -^ of this process, it is well to again call attention to a fact in 



this connection, which, if not observed, may ultimately lead to the 

 destruction of the mount. And that^is that the material of which 

 the cell is composed should be perfectly insoluble in the mounting- 

 medium employed. Patent as this may seem, it is too often forgot- 

 ten by the beginner, and even when the ill results are noticed, and 

 the cause explained, runs the danger of again being forgotten. With 

 glycerin as a medium, one has little care on this score; but with the 

 solvents generally employed with the gums and balsams, the case is 

 difiPerent. Of the cell-materials mentioned, all are more or less 

 affected by chloroform or benzol, whilst glycerin can be used with 

 perfect safety. For balsam and gum-dammar mounts, special 

 cements for building cells have been proposed. The vn'iter, how- 

 ever, has never found these necessary. The cements given in the 

 last lesson are, in his opinion, undoubtedly the best, and he has con- 

 trived to use them with any mounting- medium. The object is 

 attained by simply coating the cell with some substance insoluble in 

 the medium. With glycerin, as said, this need not be done; with 

 balsam or dammar (when dissolved in chloroform or benzol) it is 

 only necessary to coat the cell with a film of mucilage of acacia to 

 prevent any undesirable action of these solvents. This is very easily 

 accomplished. A little mucilage of the right consistency is obtained, 

 and with it, by means of. a camel's-hair pencil, the inner and top 

 portions of the cell are painted. If the operator is expert the turn- 

 table will be found convenient to do this, otherwise, it should care- 

 fully be done by hand. The mucilage should be laid on an hour or 

 two before the cell is to be used, thus allowing it to dry. If put on 

 several days before, it is liable to crack, and thus diminish its 

 usefulness. 



The process of mounting in a cell does not differ essentially 

 from the method already described whei'e no cell is employed. A 

 drop of the mounting- medium is placed in the centre of the cell- 

 space, the specimen is then lowered into the drop by means of a 

 needle (the specimen- carriers cannot be used here) and carefully 



