CHAPTER 11 



Making Smears and Squashes 



The last chapter was concerned with the preparation of microscope 

 slides from whole objects preserved as nearly as possible in their natural 

 shape; the next chapter will be concerned with the preparation of thin 

 slices of objects or "sections." Between the extremes of a whole object and 

 a thin slice, there are the types of preparation that are discussed in this 

 chapter. These are the "smear" and the "squash," which are exactly what 

 their names indicate; that is, prepared by smearing or squashing some 

 substance on a clean glass slide where it may be fixed, stained, and 

 mounted. Three operations are necessary in the preparation of smears of 

 fluids: (1) the smearing of the material itself into a layer of the required 

 thickness; (2) the fixing of this layer both to insure its adherence to the 

 slide and to make sure that the contained cells remain in their normal 

 shape; and (3) the staining and mounting of the fixed smear. Each of 

 these operations will be discussed successively. 



SMEARS 



Preparation of the Smear. The first thing to do in the preparation of a 

 smear is to make sure that there are some chemically clean slides avail- 

 able. Only materials containing large quantities of protein, such as blood, 

 will adhere to slides that are not perfectly clean. Any method may be used 

 for cleaning slides. For this particular purpose, however, the author pre- 

 fers to use any household scouring powder, which consists of a soft 

 abrasive together with some detergent agent. The powder is made into a 

 thin cream with water. Each slide is then dipped into the cream and put 

 in a rack to dry. As soon as it has dried, the slide may be returned to a 

 box, preferably separated from the next slide with a thin paper insert. 

 Since slides are commonly sold with paper separators, they may be stored 

 with the separators in the original box. 



Two or three hundred slides can be prepared easily and quickly in this 

 manner and stored for future use. When a slide is needed, the white 



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