120 



THE ART OF MAKING MICROSCOPE .SLIDES^ 



Defects 



handled in a coi)lin jar, hut it is more con- 

 venient for tliese to have an' ordinary 

 round specimen tube, or vial, of just over 

 1-inch diameter, which maintains a single 

 shde in an upright position without the 

 necessity of using the relatively large 

 quantities of fluid involved in a copUn-jar 

 set. Coplin jars are not available for slides 

 larger than 3" by 1"; for these one is 

 forced to use the rectangular jars. 



It is necessary through the subsequent 

 proceedings to be able to recognize in- 

 stantly on which side of the shde the sec- 

 tion hes. This is not nearly as easy as it 



sounds; a lot of good shdes have been lost 

 by having the sections rubbed off. The 

 simplest thing to do is to incline the shde 

 at such an angle to the light that, if the 

 section is on top, a reflection of the section 

 is seen on the lower side of the shde. A 

 diamond scratch placed in the corner is of 

 little use because it becomes invisible 

 when the slide is in xjdene. The greatest 

 care should be taken to remove the whole 

 of the wax from the slide before proceed- 

 ing further. It is usuall}^ a wise precaution 

 to have two successive jars of xylene, pass- 

 ing the second jar to the position of the 



Table 1 



DEFECTS APPEARING IN RIBBONS WHILE BEING CUT 



Fig. 71. Ribbon curved. 



Fig. 72. Sections compressed. 



Possible Causes 



1. Edges of block not parallel 



2. Knife not uniformly sharp, causing 

 more compression on one side of 

 block than other 



3. One side of lilock warmer than 

 other 



Remedies 



1. Trim block 



2. Try another portion of knife-edge 

 or resharpen knife 



3. Let block cool. Check possible 

 causes of heating or cooling, such as 

 lamps or drafts 



Possible Causes 



1. Knife blunt 



2. Wax too soft at room temperature 

 for sections of thickness required 



3. Wax warmer than room temper- 

 ature 



Remedies 



1. Try another portion of knife-edge 

 or resharpen knife. Compression 

 often occurs through a rounded 

 cuttiing facet (see Fig. 60) produced 

 by overstropping 



2. Re-embed in suitable wax or cut 

 thicker sections. Cooling block is 

 rarely successful 



3. Cool block to room temperature 



