Chapter VI: The Paraffin Method 57 



This is a frequent cause of poor staining. (&) The fixation has been 

 poor. The success of a preparation depends largely upon proper fixatiorr 

 in most cases, (c) The stain is at fault. Hematoxylin will not stain 

 properly until ripe (see Hematoxylin, page 20). Many stains, especially 

 the anilins, deteriorate and must be replaced, (d) Certain stains will 

 not follow some fixing agents. This can be remedied only by using a 

 different stain or by fixing tissues in a different fluid. The hematoxy- 

 lins and carmines are applicable after a very large variety of fixing 

 agents, (e) The paraffin has been insufficiently removed from the sec- 

 tions. This may be corrected by dissolving off the cover-glass in xylol 

 and after thoroughly removing all paraffin, restaining and mounting 

 the sections again in the ordinary way. 



14. Use Only Clean Slides and Covers. Always grasp a slide or a 

 cover by its edges to avoid soiling its surface. All cloudiness (seen by 

 looking through the glass toward some dark object) must be removed. 

 For wiping slides and covers, a piece of cloth which does not readily 

 form lint should be used. Slides may often be cleaned after simply 

 dipping them into alcohol or into alcohol followed by water. If this 

 treatment is insufficient, place them for several hours into equal parts of 

 hydrochloric acid and 95 per cent, alcohol, keeping them well separated 

 so that the liquid may act on the entire surface of each. Then rinse them 

 in water and place them in ether-alcohol. It is well to keep a stock 

 supply of such slides and cover-glasses in ether-alcohol. 



To clean a cover-glass grasp it by the edges in one hand, cover the 

 thumb and first finger of the other hand with the cleaning cloth and 

 rub both surfaces of the glass at the same time. To avoid breaking the 

 cover, keep the thumb and finger each directly opposite the other. A 

 large cover-glass may be cleaned by rubbing it between two flat blocks 

 which have been wrapped with cleaning cloths. 



To clean slides which have been used, if balsam mounts, warm and 

 place in xylol or turpentine to dissolve off the covers. Put the slides 

 and covers into separate vessels and leave them for a few days in the 

 following cleaning mixture: 



Potassium bichromate 10 parts 



Hot water 50 parts 



Sulphuric acid 50 parts 



Add the acid very cautiously after the bichromate solution cools. When 

 the slides are freed from balsam, wash them in water, rinse in a dilute 

 solution of caustic soda, again in water, and finally place them in 

 ether-alcohol until needed. 



15. If Sections Appear Milky or Hazy under a medium power of 

 the microscope, when finally mounted, the effect is probably due to one 

 of the following causes: (a) The clearer is poor and needs replenishing 

 or correcting. (6) The absolute alcohol contains water (see 7). (c) The 



