3 8 PRACTICAL HISTOLOGY. 



ing paraffin, or better still, the purified form of it named 

 belmontine, is to be preferred. The simple form of lamp, 

 devised by How of London (Fig. 36) serves very well for 



FIG. 35. Briicke's simple microscope, made by Hartnack. 



ordinary purposes. It is made with an ordinary bottle that 

 can therefore be easily replaced, if broken. A white por- 

 celain cylinder serves as a reflector, and also for cutting off 

 extraneous light from the eye. It should have a chimney 

 of white, and one of pale blue glass. 



For very high powers, especially when an achromatic condenser is 

 used, the diverging rays from the lamp must be rendered parallel by a 

 large condenser. A lamp with this arrangement is made by R. and 

 J. Beck, Ross, and others. 



The best lamp, however, for work with very high powers is that 

 devised by Mr. Dallinger, and made by Mr. G. S. Wood of Liverpool. 

 (See Monthly Microscopical Journal, vol. xv. p. 165.) The lamp is 

 expensive, but very perfect. 



52. Achromatic Condenser. This apparatus is of much 

 service in illuminating objects when very high powers are employed. 

 It may be simply made by fixing a half or quarter inch objective 

 in a tube under the stage. 



The flat surface of the mirror is used to reflect the light through 

 the object, which must be arranged so that the light is focalised on 

 the object. Special forms of this instrument, with diaphragm, having 

 apertures of various sizes and shapes for giving different illuminating 



