i8o THE MICROSCOPE. 



pletely obliterated when placed in balsam or other media of a high 

 refractive index, that it becomes necessary to find others, which, at 

 the same time, will properly preserve the tissues and best exhibit 

 their structures. I do not propose to give any formulae for the 

 preparation of these (numerous excellent ones for all purposes may 

 be found in the vari6us manuals on the microscope by different 

 eminent writers), but shall confine my paper to practical hints, as 

 to the best methods of using the fluids and rendering the mounts 

 permanent. 



For this has been the stumbling block in the way of many who 

 would gladly mount their specimens in this way, but for the appar- 

 ent difficulty of doing so permanently. " Oh, my fluid mounts all 

 leak and are ruined in a few months," or, "I cannot make a fluid 

 mount without air bubbles, and so don't bother with them," are 

 remarks I have heard over and over again, and can appreciate 

 the truthfulness of same, for did I not wallow through the same 

 slough for years? The books, for instance, gave me no real aid. 

 They were misleading and unsatisfactory. Quekett (my first, and 

 therefore best remembered authority, whose well thumbed work lies 

 before me), says: "Thei^^i-/ method for mounting in fluids is as 

 follows: Take a slip of thin plate glass, lay it flat and place a 

 drop of the preservative fluid to be used upon it in the centre; in 

 this the object is laid, and after having been properly spread out 

 with the needle point, it is ready to receive its cover of thin glass. 

 The edges of the cover should be touched slightly with the cement 

 to be used and then laid upon the object, which is effected by drop- 

 ping the cover gently upon the fluid and pressing it lightly, to 

 exclude the excess and to leave only a thin stratum intervening 

 between the two glasses; the excess may be removed by small slips 

 of blotting paper. After this operation is finished a thin layer of 

 cement is to be placed where the edges of the cover come in con- 

 tact with the bottom glass; when this is dry another thin layer may be 

 put on, until the angle between the two glasses is nearly filled up. 

 Care must be taken to exclude all air bubbles from between the 

 cover and bottom glass, otherwise the cement will run in, especi- 

 ally when the bubbles are near the edge." He then naively adds: 

 '■'■Objects 7nountcd in this way seldom keep very long," to the 

 truthfulness of which many a poor fellow as well as myself can 

 testify. 



