6s8 



LABORATORY EXERCISES. 



The Edinger drawing and projection apparatus^ (Figs. 234, 235) projects micro- 

 scopic objects even under a high magnification directly upon the drawing board so 

 that the outline can be traced in pencil. The image thus projected can be used for 

 demonstrating to a small audience and also for photomicrography. For such work 

 a powerful illuminant is used with a hand-fed electric arc taking 4 amperes. It may 

 be used with a suitable plug connected with the direct-current house supply (alter- 

 nating current may be used by special arrangement). The crater in the positive 



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 Fig. "232. — Clinic microtome with freezing attachment. 



carbon from which light emanates is brought to coincide with the optic axis of the 

 apparatus by means of the two screws (o) as in Fig. 234, and the lamp with the con- 

 densing system K can be moved along the optic axis by the lever G. The distance 

 between the carbons is regulated by the milled head (6) which if out of reach of 

 the operator can be turned by the long handle connected to (c). The smaller car- 

 bon which is placed horizontally should not project into the optical axis, or crater 

 area of the larger vertical carbon. 



The apparatus proper consists of a cast-iron pillar S, Fig. 234, mounted upon a 

 1 May be had of E. Leitz, 30 East icSth Street, New York City. 



