7(!0 HISTOLOGIC TECHNIC 



traces of 'milky' appearance. The following oils are commonly used 

 for clarification: Bergamot, origanum cretici, cajuput, clove, carbo- 

 xylol. Xylol carbolic acid, melted, 25 to 33 c.c. ; xylol, 75 to 67 c.c.), and 

 xylol. Xylol (xylene) is the most desirable in that it is perfectly miscible 

 with the balsam in which the section is usually mounted, and is finally 

 lost by evaporation. It will not act in the presence of the least trace of 

 water. Carbo-xylol has the advantage of a slight affinity for water; 

 this is also true of the heavier oils. Complete dehydration is therefore 

 not required. Bergamot is desirable for celloidin sections, but has {he 

 disadvantage of rapid deterioration, after which it dissolves the celloidin. 

 Either origanum or cajuput oil, or a mixture of the two, serves well for 

 celloidin sections, but leaves them somewhat stiffer than does bergamot 

 oil. The latter is therefore preferable for elastic tissues. On the whole, 

 origanum serves best for routine work with celloidin sections, xylol or 

 carbo-xylol for paraffin. 



After clarification celloidiu sections must be transferred to a slide. 

 This is accomplished by means of a metal lifter or by a strip of rice 

 paper (ordinary cigarette paper does nicely). The section, lying on the 

 paper, is inverted upon the surface of the slide, to which it remains 

 adherent after the paper is gently lifted. The excess of oil is then 

 removed with blotting paper or by gentle pressure with a folded towel, 

 a drop of xylol-balsam applied, and the cover glass dropped into position. 

 The preparation is permanent. 



Xylol-balsam is prepared by adding to Canada balsam sufficient 

 xylol so that the mixture will have a thick, syrupy consistence, but will 

 drop from a glass rod without stringing. 



Sections may also be permanently mounted in glycerin without pre- 

 vious dehydration, the edge of the cover glass being, after some hours, 

 covered with a ring of King's cement. 



Glycerin jelly is also serviceable, and does not require cementing of 

 cover glass. 



Neutral Balsam. Sections may frequently be rendered more per- 

 manent by the use of neutral balsam, prepared as follows : 



Dilute Canada balsam with xylol until it acquires a very thin watery 

 consistence. Add sodium bicarbonate in excess. Shake thoroughly, and 

 allow to stand in a stoppered bottle for twelve hours or more. Filter; 

 this is readily, though slowly, accomplished if the dilution is sufficient. 

 Permit the solution to stand in an open vessel, protected from dust, 

 until it evaporates to the proper consistence for use. 



Gum-Damar. This material, also dissolved in xylol, is in some re- 



