I 4 6 PRACTICAL HISTOLOGY. 



close to the slide, so that the lamp may be removed the 

 moment the temperature becomes unpleasant to the touch. 



FIG. 47. Simple hot stage. 



260. Strieker's hot stage. Max Schultze was the first to in- 

 vent an apparatus for keeping a microscopic object at a constant 

 temperature. His instrument, however, was not very convenient, and 

 modifications of it have therefore been devised. Strieker's hot stage 

 (Fig. 48) is one of these. It consists of a rectangular piece of ebonite 

 fixed on a brass plate that rests on the stage of the microscope. On 

 the upper surface of the ebonite there is a copper disc, with an aperture 

 (c) leading into a short metal tube closed inferiorly by a piece of glass. 

 The object to be heated is placed between two cover-glasses and laid 

 on the disc, a ring of olive or almond oil is then painted around the 

 cover-glasses to prevent evaporation. For heating the object, a thick 

 copper wire (w), coiled at one end, is stuck upon the copper tube (a), 



FIG. 48. Strieker's hot stage and gas chamber. 



by the wall of which the heat is conducted to the copper disc. The 

 wire is about six inches long, and is heated by a spirit lamp or gas- 

 burner placed on the table in front of the microscope. The temperature 

 depends on the distance of the point of application of the flame from 

 the stage, and on the proximity of the flame to the wire. The tempera- 



