He should be able to bring the performance of the 

 objective up to the claims made for it, if it has come 

 from the hands of a reliable optician, and should not 

 rest until this is accomplished. 



The writer has often recommended sunlight with 

 generally * successful results where ordinary means of 

 illumination have failed. The light is of course intense 

 and great care will have to be used to modify it by 

 properly using the mirror, but success is often attained 

 and then creates confidence. It is, however, only 

 recommended for this purpose and not for general use. 



Stained Bacteria and Micrococci also make excel- 

 lent objects for immersion objectives. The mode of 

 illumination is the same as with dry objectives. Great 

 care and judgment should, however, be exercised in 

 forming an opinion as to resolving power from such 

 specimens. Only the most carefully stained and suit- 

 ably selected specimens are of any value, among the 

 best of which may be mentioned the beaded form of 

 Bacillus tuberculosis, if clearly and deeply stained. 

 The enveloping structures of many bacteria and the 

 diffusion of stain from them to the surrounding sub- 

 stances in which they are imbedded render them 

 entirely useless for test purposes. 



Opaque Objects are so dense in their structure 

 that the light from the mirror below the stage will not 

 pass through them. They generally consist of plants, 

 minerals, shells, etc. 



