58 



THE MICROSCOPE 



Mounting 

 specimens. 



Turntable. 



Hema- 

 cytometer. 



which can then be reversed in its fitting so that either the forceps 

 or the cork can be brought into the centre of the field ; they can 

 also be rotated so that all parts of the object they hold can be 

 examined. This apparatus is useful for the examination of small 

 insects, botanical specimens, fragments of rock, tissues, and other 

 small solid bodies. 



A case can be supplied containing apparatus for holding 

 objects, which includes 3 X 1-inch slips, a slip with ledge, a slip 

 with hollow, a trough on slip, a Beck glass trough, a live box, 

 a Beck compressor, stage forceps," and a supply of thin glass. 

 The Rousselet live box is not included, as it is not of the standard 

 3 X 1-inch size. 



Mounting permanent specimens for the microscope is a subject 

 that is beyond the scope of this book. The microscopist should 

 be provided with a bottle of Canada balsam dissolved in benzol 

 or xylol, which is a transparent cement, and a bottle of Hollis glue, 

 which is a brown shellac cement. Many objects can be mounted 

 by means of these two cements. Small shells, botanical and 

 entomological specimens, diatoms, and other small objects may 

 be attached to a 3 X 1-inch sUp with gum or Canada balsam inside 

 a cell of paper, vulcanite, or glass of a thickness sufficient to 

 protect them, and with a cover glass cemented to the cell. A 

 narrow ring of cement of the diameter of the cover glass, dried 

 upon the slip, is often sufficiently thick to protect small objects 

 when a cover glass is cemented to the surface of this ring. 



A turntable (Fig. 59) is an appliance for making rings of 

 cement on a 3 X 1-inch glass slip and for placing a protecting ring 

 of cement round a circular cover glass or 

 cell after it has been cemented on. The 

 slip is held on to the circular revolving 

 table by spring clips, and by holding a 

 camel's-hair brush, which has been dipped 

 into cement, against the slip as this table 

 spins round, a layer of cement is left 

 in a neat circular ring. 



Many objects can be placed on a slip and a drop of Canada 

 balsam dropped upon them, a cover glass being then placed over 

 the drop before it has set. The specimen is thus permanently 

 preserved. This is all that is required with such specimens as 

 dried blood films or stained bacteria. 



It is essential, however, that such specimens should not be 

 moist, as water wUl not mix with Canada balsam, and some objects 

 require to be first soaked in absolute alcohol or turpentine to 

 remove the water or air. 



The hsemacytometer is an apparatus for counting the blood 

 corpuscles, and consists of a counting chamber, two mixing pipettes, 

 and suitable optically plane cover glasses. The blood is first 

 diluted with a solution known as " Toisson's " solution, for either 



Fig. 59.— No. 3386, 

 Turntable. 



