INTRODUCTION 243 



The approximate magnifications afforded by the various combinations 

 are as follows : 



Eyepiece * X Objective l = diameters magnification. 



X 



" w u a it 



X 



When a very low magnification is desired, as for example in the study 

 of a large opaque object, the simple dissecting microscope is used. It 

 gives a magnification of about 10 diameters. 



6. At the close of each exercise be sure to remove the slide that you have 

 been studying from the stage of the microscope. Examine the microscope 

 carefully and make sure that all parts, including the lenses, are perfectly 

 clean and then return the microscope to its proper place in the case. 

 Remember that since there are others who must use the same microscope, 

 the welfare of the laboratory depends upon your cooperation in keeping the 

 apparatus in order. 



C. Microscopic Preparations 



7. The preparations which will be examined with the compound micro- 

 scope may be divided into two classes as follows : 



(1) Permanent preparations in which the material to be examined 

 has been previously subjected to complicated histological methods for 

 preserving, staining, and permanent mounting on a glass slide. Great care 

 must be observed in handling these preparations. A charge will be made 

 for breakage. 



(2) Temporary preparations which you will make when necessary by 

 mounting the material to be examined on a glass slide according to the 

 following directions : 



(a) Thoroughly clean a glass slide and cover glass. 



(b) Place a small drop of water in the center of the glass slide. 



(c) Place the object to be examined in the drop of water. 



(d) Cover the drop of water containing the object with the cover glass. 



(e) Remove any superfluous water remaining around the cover glass 



with the absorbent filter paper. Be sure that no water gets on to 

 the upper surface of the cover glass. The preparation is now 

 ready to be studied under the microscope. 

 (/) When you have finished your study of a temporary preparation, 

 clean the slide and cover glass, and replace them in the drawer for 

 future use. 



D. Laboratory Drawings 



8. It is essential that careful attention be paid to the following rules for 

 laboratory drawings : 



1 Numbers will be supplied by the instructor. 



