APPARATUS FOR HOLDING SPECIMENS 



57 



is held between the two glasses. This appliance is useful for 

 examining living insects or for flattening out thin, uneven objects, 

 such as a piece of a leaf or 

 fabric. It is chiefly used with low 

 powers, as substage illuminating 

 apparatus cannot be readily used. 

 A form of live box known as 

 the Rousselet live box is useful for 

 high powers. The principle is that pie. 66.— No. 3420, Live Box. 

 of an ordinary live box, but the 



fixed lower glass plate is on the level of the stage, and a 

 substage condenser or high-power illuminator can be used with 

 this live box. When a very small object is to be examined, a 

 still smaller cover glass may be cemented with Canada balsam 

 to the centre of the lower glass plate, and the object is thus 

 confined to the centre of the field. It is 2| X If inches, and is 

 not suitable for use on a mechanical stage. 



The Beck compressor is a 3 X 1-inch plate of glass at one end Compressor, 

 of which a circular pillar is fixed. This pillar carries an arm 

 which holds a thin cover glass 3/4 X If inches. The arm is 



raised or lowered by a screw 

 at the top of the pillar, which 

 mechanically varies the space for 

 holding the specimen. The arm 

 carrying the thin glass can be 

 swung to one side for placing the 

 specimen in position and then 

 lowered to the required amount. 

 For many purposes this compressor is more convenient than a 

 live box, for by means of the delicate screw motion a living object 

 may be held stationary without being crushed. Also, the slip 

 being made of glass, it can be kept clean, and the thin glass which 

 is attached to the arm by spring clips can be readily removed 

 for cleaning, or replaced if broken. It can be used with substage 

 condensers and dark-ground illuminators. 



A convenient method of holding small solid objects for stage 

 observation imder the microscope is by means of a pair of stage '<"^<=^p^' 

 forceps, which are attached to a 3 X 1-inch ebonite plate. The 

 plate is either held by the niechanical stage or, if the microscope 

 is not fitted with the latter, 

 by means of the spring stage 

 clips. On the plate is a 

 metal fitting holding a rod, 

 which has at one end a small 

 pair of spring forceps opened 

 by pressing the two pins 



together, while at the other end is a cork into which specimens 

 may be pinned. The forceps can be unscrewed from the rod. 



Fig. 57.— No. 3421, Beck's 

 Compressor. 



Fig. 58.— No. 3422, Stage Forceps. 



