PRACTICAL HISTOLOGY. 



Body. 



Body tube. 



mode in which this is accomplished varies. In the cheaper 

 microscopes the tube of the microscope is moved inside another 



tube fixed to the 

 Eye-piece. stand (fig. 9). This 



is done by means of 

 the hand, while in 

 the more expensive 

 microscopes there is a 

 rack-and-pinion move- 

 ment for raising or 

 depressing the tube 

 (fig. 10). 



Usually there are 

 two adjustments one 

 the coarse adjust- 

 ment, whether it be 

 by rotating one tube 

 inside the other or 

 by a rack-and-pinion 

 movement ; it is used 

 to bring the outlines 

 of the object dimly 

 into focus. The other, 

 the fine adjustment, 

 is a fine screw, usually 

 placed at the upper 

 and back part of the 

 pillar of the stand of 

 the microscope. By 

 it the object is brought 

 accurately into focus. 

 4. The stand is pro- 

 vided with a hori- 

 zontal solid table or 

 stage, placed at a con- 

 venient height, and 

 on which the object 

 to be examined is 

 placed. The stage 

 consists of a flat plate 

 of brass blackened on 

 its under surface, or 

 There are two clips 



Stage. 



FlG. 9. Leitz's Microscope, No. V. 



of a glass plate fixed on a black ground. 



which are used for fixing a preparation in a definite position on the 



stafe. It is perforated by a circular aperture in its centre, into 



