The Complete Substage consists of a vertical 

 bar fixed to the microscope in place of the mirror bar 

 and having an adjustable slide x operated by rack 

 and pinion a, carrying supporting attachments for upper 

 iris diaphragm, condenser and lower iris diaphragm 

 respectively, and at its lower end the plane and concave 

 mirrors m. 



Fig. 51b. Complete Substage. Front view, with condenser and lower 

 iris diaphragm swung out of optical axis. 



The Upper Iris Diaphragm e is carried in the 

 upper substage ring s. In use it is opened and closed 

 V^y the lever / and serves to regulate the amount of light 

 when an object is viewed without the condenser and 

 to limit the volume of light without reducing its angle 

 when the condenser is used with extremely transparent 

 objects, such as unstained bacteria, moulds, etc. It is 

 raised and lowered by the pinion a which moves the 

 whole substage. 



'57 



