THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



Vol. XIII. 



APRIL, 1892. 



No. 4. 



COKTB JVTS 



The Abbe Illuininator or Con- 

 denser (Illustrated). — Gage - 



Acknowledgment 



Practical Studies in Biology. — I. 

 The Potato.— OsBORN - - - 



Use of the Microscope in Phar- 

 mac}'. — Whei-PLEY - - - - 



An All-around Microscope (Illus- 

 trated). — Forbes 



Magnifying Power of Objectives. 



— TOLMAN ------- 



A New P'rame for the Pocket Mi- 

 croscope (Illustrated). -Sayre. 



Editorial 



Microscopical Apparatus . — 

 New Objectives. The Bacterio- 

 logical Star Microscope 



Microscopical Manipulation. 

 —A Paper for Cleaning the 



Lenses of Objectives and Ocu- 

 lars. Glue for Labels. Use of 

 Hydroxylamine ----- qq 



Biological Notes. — Senega. 

 Scarlet Clover. A Circular 

 Growth of Fungus. Attach- 

 ment of VorticelliL' - - - - loi 



Bacteriology.— A Bacteriologi- 

 cal Examination of the Boston 

 Milk Supply. A New Bacte- 

 rium. Bacteria in Street-dust. 

 Sewage -------- 103 



Microscopical News. — Death 

 of L. D. Mcintosh. White's 

 Objects -------- 103 



Correspondence. — Spencer & 

 Smith's Aplanatic Eye-Piece. 103 



Microscopical Societies. — 

 San Francisco. St. Louis. 104 



The Abbe Illiimiiiator or Condenser 



By Prof. S. H. GAGE, 



ITHACA, N. Y. 



[From The Microscope and Histology-.] 



For all powers, but especially for high-power objectives, a con- 

 denser or illuminator is of great advantage. The one most gen- 

 erally useful was designed by Abbe. It consists of two or three 

 very large lenses which are placed in some form of mounting be- 

 neath the stage. It serves to concentrate a very wide pencil of 

 light from the mirror upon the object. For the best work in 

 modern histology the Abbe illuminator is almost as indispensable 

 as the homogeneous immersion objectives. 



Centring and Arrangement of the Illuminator. — The 

 proper position of the illuminator for high objectives is one in 



