488 MANIPULATION. 



Brooke cements the cell to a slide of slate with a hole in the 

 centre. 



Thin Glass Cells. — These may be very expeditiously made, 

 by compressing a piece of thin glass between two surfaces of 

 wood or brass, having a hole in them, the intended size of the 

 cell. When the thin glass is fixed between these, it should 

 be scratched round the interior of the hole on both sides with 

 a diamond, and then the centre may be pushed out. 



Opaque Objects in Fluid, such as injected preparations, 

 which require to be looked at on both sides: the cells are best 

 made by drilling a round hole in the slide itself, and cement- 

 ing a piece of thin glass on one side of it with marine glue ; 

 when the object is introduced, another piece of thin glass is to 

 be cemented on the other side with gold size or liquid jet in 

 the usual way. 



New Method of Cementing Cells. — Cells for containing dried 

 injections or other preparations in turpentine, may be cemented 

 with common carpenter's glue, which will effectually prevent 

 the escape of the turpentine. 



Mr. Brockets Arrangement for Erecting the Object for Dis- 

 section and for Drawing. — For this purpose a rectangular 

 prism is interposed between two pieces of tube, meeting at an 

 angle of 100°, one of which enters the body of the microscope, 

 and the other receives the eye-piece. By this arrangement 

 the object is inverted in the plane in which the angle of the 

 tubes lies; but in order to erect the object, it is necessary also 

 to invert it in a plane at right angles to the former — this is 

 effected by placing a small rectangular prism edgewise in 

 front of the eye-piece. 



For drawing the object, a small prism, having two parallel 

 polished sides, is placed in front of the eye-piece in place 

 of the rectangular prism, so that while the object is seen by 

 reflection at an angle of 45" from the surface of the prism, 

 the paper placed on the table is seen directly through the two 

 parallel sides. By this second reflection the object is rein- 

 verted in the same plane, and is therefore seen and drawn 

 correctly. 



