CHAPTER 4 



Types of Microscope Slides 



The equipment described is used to make four main types of microscope 

 slides. These are wholemounts, smears, squashes, and sections. Examples 

 of each are given in detail in Part Three and it is intended here only to 

 provide a brief summary to which the beginning student may refer. 



Wholemounts. These, as the name indicates, are mounts of whole ob- 

 jects so preserved that the structure can be studied. Such objects must 

 first be killed and fixed to preserve them in the shape they had in 

 life. Contractile animals must be narcotized, even before this is done. 

 The fixed material must then be washed, to rid it of the reagents used 

 in fixing, and may be preserved in 70 per cent alcohol. Material of this 

 type is opaque so that, viewed under the microscope, it would appear 

 only as a silhouette. It may be rendered transparent by soaking it in oil, 

 a process which must naturally be preceded by the removal of water. This 

 is accomplished by soaking the objects in alcohol. The "oil-cleared" 

 specimens may be examined in this condition or, more usually, impreg- 

 nated with a resin that preserves them as an insect is preserved in amber. 

 Many things are by this process rendered too transparent for convenient 

 study so that they are, before clearing and mounting, stained in dyes, 

 the better to show their internal structure. A few organisms are so tough 

 that they may be placed directly in water-soluble gums for permanent 

 preservation. This process of wholemounting is shown in diagrammatic 

 form below. 



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