MOUNTING SECTIONS CUT IN PARAFFIN. 15 



guidance. Heat again if necessary until the melting point is reached 

 and apply the solvent. Dry the slide with blotting paper, apply balsam 

 and cover. 



2. If the section is to be stained 1 remove the solvent with absolute 

 alcohol. Any trace of paraffin remaining in the section will appear 

 white, spicular under the microscope, and must be removed. Then 

 having bathed the preparation with a drop of water, to be certain that 

 it will wet uniformly, apply the staining reagent. 



3. Flattening on Oil. Crumpled sections which do not require fixing 

 to the slide are most conveniently treated as follows : A pool of the 

 essential oil used for clearing (cedar oil when eosin is present) sufficient 

 to float the section is placed upon the slide and is slightly warmed. 

 The section is floated upon it and flattens. The superfluous oil is 

 drained off with blotting paper, additional heat is applied just sufficient 

 to melt the paraffin, drain, add more of the oil to dissolve what remains 

 of the paraffin, cool and if no paraffin is visible add balsam and cover. 



If the sections are extremely thin and tend to fall apart when the 

 paraffin is melted employ one of the following methods : 



4. Shellac fixation. For stained sections. Smear a very thin film of 

 a saturated solution of white shellac in creosote with your finger on the 

 middle of a slide, place the section in position and press it lightly into 

 contact with the fixative with a dry finger. Melt the paraffin over the 

 burner, being careful not to heat beyond the melting point ; keep it 

 melted for a minute, drain off and dissolve away the remaining paraffin 

 with turpentine or toluene, apply balsam and cover. 



5. Water fixation. For sections ivhich are to be stained upon the 

 slide (Gulland.) If the section is curled or frilled, place it on warm 

 water, not above 40 C ; it will flatten. Float on to a slide or cover- 

 glass, arid blot off the water thoroughly. Heat to the warmth of the 

 hand for ten minutes over the bunsen flame to drive off all moisture, 

 then heat sufficiently to melt the paraffin. The section will adhere to 

 the slide. 2 Use turpentine to dissolve the paraffin, blot off the excess, 

 add balsam, and cover. Unstained sections after being freed of tur- 

 pentine or toluene by means of alcohol can be stained in position upon 

 the slide. 



1 These operations can be performed upon a large number of sections at a time 

 in a watch glass or porcelain capsule. Heating unnecessary provided sufficient 

 solvents and time are given. 



2 24 hours drying at the ordinary temperature and shielded from dust is more 

 certain. The slides must be perfectly clean and free fiom grease. It is best to 

 clean them with alcohol before use. 



