826 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



being parallel to the knife-blade), and the bent arm of tbe axis of 

 the glass cylinder passes into it and is clamped by tbe screw h. By 

 the screws i and i' the block h can be raised at one end and depressed 

 at the other, thereby raising or lowering the cylinder a above the 



knife-blade. The maximum length 

 Fig. 143. suggested for the cylinders is 5 cm. 



and the diameter 4, 6, and 9 mm. 



Griffith's Turntable. — Mr. 



mi^^^m^tFi ^- H* Grriffith has devised the in- 



^^^^^M|| geniously simple turntable shown 



raogm-^ MaiiillllllililF in fig. 14:3. 



The centre of the table, marked 

 with the circles, has a spiral spring 

 attached to it beneath. The slide 

 being placed between the two pins 

 ^^^^^ in this centre, is partially rotated 



^ ^ against the spring and pushed for- 



ward, when the spring keys it be- 

 tween the two pins and a third 

 fixed pin at the upper side of the 

 slide (towards the left). The fourth 

 pin, at the left end, is for length. The table rotates on a pointed 

 spindle, and can be lifted off it as required. 



Reversible Mounts.* — Of late years much attention has been 

 given to the preparation of whole insects, without subjecting them to 

 pressure, by using cells of vulcanite or other suitable substance 

 afiBxed to the ordinary slides. T. J. Briant has in the same way 

 put up tMck sections of various parts of insects with very good results. 

 Such preparations allow of the examination of the various parts as 

 they are arranged in the body of the insect, and are comparatively 

 easy to make, either by the ordinary section-cutter or by hand. It 

 is, however, frequently found, both in the case of whole insects as 

 well as that of the thick sections, that one wants to know the appear- 

 ance from the opposite side. Of course the slide may be turned over, 

 but the critical examination of an object through glass of the thickness 

 of an ordinary slip is very difficult — practically impossible. 



In order to overcome this difficulty take a vulcanite ring and 

 fasten a thin cover as a bottom to it with any good cement ; fill it 

 with balsam, immerse the preparation, and cover with another thin 

 cover. Then put this aside to dry, placing it on the top of a small 

 cork fixed in a bottle, and thus preventing the superfluous balsam 

 fastening the ring to the shelf or table. The ring with its cover and 

 contents is then placed in a wooden slide, with a hole corresponding 

 in size to that of the ring. Usually there is enough balsam around 

 the edge to hold the ring in place, but if not the slip may be covered 

 on both sides with paper. In the case of small objects, two glass 

 covers may be used, kept apart by small pieces of thin glass cover ; 



* Thirteenth Ann. Rep. South London Micr. and Nat. Hist. Club, 1884, 

 p. 13. 



