118 



PRACTICAL HISTOLOGY. 



[in. 



to have a layer of diluted blood in a thin film between the two 

 cover-glasses, and exactly filling the space between them. Any 

 surplus fluid at the edge of the cover- 

 glasses must be removed by blotting-paper. 

 With a camel's-hair pencil then run a layer 

 of oil round the edge of the smaller cover- 

 glass, or the preparation may be sealed up 

 with melted paraffin wax. This will pre- 

 vent evaporation. The larger cover-glass 

 acts the part of a slide. 



Fix the warm stage on the stage of the 

 microscope by means of the clips on the 

 microscope, and over the aperture in the 

 warm stage place the cover-glasses. Focus 

 the corpuscle between the two cover- 

 glasses, and notice that the colourless 

 ones do not exhibit amoeboid move- 

 ments. 



Heat the projecting rod by means of a 

 spirit-lamp. The heat travels along the 

 copper, and finally warms the cover-glasses 

 and the layer of blood between them. It 

 must, however, not be overheated. In 

 order to prevent overheating, make pre- 

 viously a mixture of cacao-butter and 

 white wax, which melts at 38 C., and 

 place a fragment of this on the copper 

 stem near the copper plate. Heat should 

 be applied until the wax just begins to melt. 



Observe the colourless corpuscles when heated beginning to 



FIG. 75.- Simple Copper Warm 

 Stage. 



FIG. 76. Warm Stage made by Reichert of Vienna. It costs i. A, A'. Screws to fix it 

 to the stage of a microscope ; B. Inflow, and 15'. Outflow of water. 



exhibit amoeboid movement. Sketch a corpuscle, and in a few 

 minutes make another sketch and compare the two. 



