48 



(6) If the sections formed are forced together 

 (telescoped) the paraffin is too soft. 



(c) A certain amount of crinkling is usual 

 with thin sections, and can subsequently be got 

 rid of before mounting. 



To Embed Tissues- 



1. Alcohol. — Two to three hours, using dehy- 

 drated alcohol (vide antea) in excess, and changing 

 two to three times. If soft tissues, e.g., liver, 

 spleen, time is unimportant so long as dehydration 

 is complete. If fibrous organs, the least possible 

 time that will ensure dehydration (using ' thin 

 slabs). Fibrous tissue becomes excessively hard if 

 left too long in alcohol, xylol, or paraffin ; thus 

 skin and connective tissue require great care in 

 preparation. 



2. Xylol (or oil of cloves). — Ten to twenty 

 minutes. When the tissues become transparent 

 they are ready, and should be transferred without- 

 delay to melted paraffin. 



3. Paraffin. — Ten to thirty minutes. If a 

 tin trough be used, the tissues should not be 

 allowed to rest upon the bottom of the trough, 

 but be supported upon a strip of paper kept in 

 place by folding the ends over the edge of the 

 trough. A watch glass generally suffices. • 



4. Prepare a block for cutting by one of the 

 following methods : — 



(i) If the piece of tissue be small, smear a 

 watch glass with glycerine, fill with melted para- 

 ffin and add the piece of tissue picked out of the 

 bath with forceps, warmed by passing through 

 the flame. 



