01' THE MICEOSCOPE. 187 



PREPARATION, PRESERVATION AND MOUNTING OF 

 OBJECTS. 



These three operations are so frequently applied as a single 

 process to objects, that many writers have failed to make a suf- 

 ficient distinction between them. By keeping the proper dis- 

 tinction clearly in mind, however, the student will not only 

 save much valuable time, but he will secure vastly better re- 

 sults. Except by those who are more anxious to increase the 

 number of objects in their cabinet than the amount of know- 

 ledge which they possess, a very large proportion of the ob- 

 jects examined will never be preserved or mounted at all. This 

 however, should not prevent the utmost care being given to the 

 process of preparing them for thorough examination. On the 

 other hand it often happens that objects which have been 

 carefully prepared and mounted, spoil because they have not 

 been subjected to a proper preserving process. Hence the 

 importance of treating these operations separately and fully. 



The Preparation and Examination of Objects. 



It is a common but very erroneous idea that the only thing 

 that is necessary in order to examine any object under the mi- 

 croscope, is simply to place it on the stage, and get it into 

 focus. With the exception of mounted objects, a very few 

 transparent objects such as the wings of insects and some 

 things that are viewed by reflected light, every substance re- 

 quires to undergo careful preparation before it can be fit for 

 profitable examination. A good example of the necessity for 

 such preparation is seen in the common potato, a piece of which 

 when simply placed on the stage of the microscope, and brought 

 into focus, appears as a glistening mass, and reveals nothing of 

 its true structure. If we now cut from this lump, by means of 

 a very sharp knife, an exceedingly thin slice, place it on a 

 plate of glass, moisten it with a little spirit and water, or better 

 still, glycerine and water, and place over it a thin glass cover, it 

 will disclose to us a most wonderful and beautiful structure. The 

 entire mass will be seen to be composed of cells, these cells be- 

 ing filled with granules of starch of various sizes. 



