■ 



E. beitz, optical works, Uletzlar. 



New-YorR 



30, East 18th Str. 



Berlin NW. 



Luisenstrasse 45 



Branches : 



Chicago 



360 Ogden Avenue 



Frankfort o. M. 



Neue Mainzerstr. 24 



London W. 



9—15 Oxford Str. 



St. Petersburg 



Woskressenski 1 1 



Reflecting Condenser for Observing Living Bac- 

 teria etc. under Dark Ground Illumination. 



Reflecting Condenser A. 



This Reflecting Condenser, which was originated by Mr. W. 

 v. Ignatovvsky, a member of the scientific staff of the firm, was 

 fully described in the Zeitschr. f. wiss. Mikr., Vol. 25, 1908, No. 1. 

 It serves for observation under dark-ground illumination, and 

 more especially for bringing into view living and unstained bacteria. 



This mode of illumination derives its success from the contrast 

 produced between the intensely illuminated bacteria and their dark 

 surroundings. Two reflecting surfaces, one internal, the other 

 external, as shown in the figure, are so shaped as to almost 

 completely unite the rays in a point P, and, by reducing the 

 astigmatism to its lowest limits, gives rise to an intense illumina- 



