504 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



the rear lens. Leitz' immersion objectives are particularly convenient 

 for this arrangement. The effect is to make the objects (e.g. bacteria) 

 appear bright on a dark ground even with the strongest ocular magni- 

 fication. 



Fig. 94. 



Fig. 95. 



Leitz' Universal Projection Apparatus.*— This apparatus is adapted 

 for diascopic, microscopic, and episcopic projection, the last being 



Fig. 96. 



attainable with either downward or lateral illumination. The essential 

 characteristic in all is that, owing to direct illumination of the object, 



* Catalogue, No, 41 (Mikroskope) 1905, pp. 91-4. 



