INTRODUCTION. 



E. Hartnack, Potsdam. 



0. Reioherfc, Vienna. 



B. LeitZj Wetzlar. 



L. BenSche, Berlinj S.W., Grossbeeren Straasse, 19. 



J. Kldnne & Miiller, Berlin. 



P. W. Schieck, Berlin. 



Schmidt & Hanscli, Berlin, S. 



R. Winkel, Gottingen. 



P. Plossl & Co., Vienna. 



A. Nachet, Paris, rue St. Severin, 17. 



It is sufficient for all ordinary bacteriological work 

 to have a simple microscope, with six different objec- 

 tives, magnifying about 50, 100, 200, 500, 700, 1,000 

 diameters ; it is also well to have an illuminating ap- 

 paratus, and, if possible, an oil immersion lens. Prom 

 my own experience, I can recommend the following 

 as good combinations : — 



Zeiss, Stand 6. Illuminating apparatus No. 19, 

 Lenses A, D, and -jV homogeneous immersion. Eye 

 pieces 2, 3, and 4, price £16 2s. 



Seibert, Stand 4. Small illuminating apparatus. 

 Lenses I., V., and X. Eye-pieces I., II., III., price 

 £16 16s. 6d. 



Other manufacturers supply similar instruments 

 at somewhat lower prices; however, their instru- 

 ments scarcely reach the excellence of those sup- 

 plied by the above well-known firms. Unless the 



