IO 
PHARMACEUTICAL BOTANY 
designated by numbers or by figures, as e t c -> or in milli¬ 
meters, as 2 mm., 4 mm., 16 mm., which represent focal lengths. 
The smaller the number or fraction representing the focal length 
of an objective, the greater is its magnifying power. 
Body Tube 
Graduated Short Slide - 
Devolving 
Stage- 
Adjustable 
Spring Finger 
Condenser Mounting on 
Drop Swing Arm.--' 
Lower Iris Diaphragm 
for Oblique Light. 
Stage Centering Screws 
Mirror- 
Mirrqir Forr> 
Mirror Bar 
Rack & Pinion 
Button 
-Rack & VInibn 
Coarse Adjustment 
Fine Adjustment 
Buttons 
Concentric Adjust 
Buttons 
Graduated Long 
Slide 
-Arm 
Inclination Joint 
Horseshoe 
-Base 
-Draw- Tube 
Fig. 3.—Illustrating the parts of a compound microscope. 
Objectives are either dry lenses or immersion lenses. If an air 
space be present between the objective and the object, the lens is 
called a dry one; if a liquid is present between the objective and the 
object, the lens is called an immersion lens. If this liquid be oil, 
