n6 ELEMENTARY TECHNOLOGY. 



By dissection with needles, in fluid. By shaking in test 

 tube with fluid. By pressure under cover glass (com- 

 pre ssor). 



jr. Making sections. 



For bone, teeth, etc., use fine saw, then cement on slide and 

 file down, hone and polish. For softer tissues extemporane- 

 ous sections may be made by scissors curved on the flat, Valen- 

 tin's knife, razor or scalpel. 



The microtome or section cutter is used when accuracy or 

 many specimens are required. Elevate the object by screw or 

 inclined plane, or both. The freezing microtome is sometimes 

 used. 



Hand sections. Keep back of knife to operator. Draw ob- 

 liquely from heelto point razor,(if vice versa}. Dexterity is 

 gained by practice. Always keep the knife wet with water or 

 alcohol, and manipulate sections with a camel's hair pencil. 



Imbedding serves to hold small or brittle specimens for cut- 

 ling. 



1. In pieces of carrot, potato, etc., for hard sections, as of 

 softened bone, or hardened cord. 



2. In elder pith. After placing the specimen and binding 

 with thread it may be held fast by placing in water. 



3. In paraffine, 5 parts to one of lard. A little clove oil ren- 

 ders it less liable to stick to the knife. Melt in water bath at 

 low temperature. Pour into paper cone or box or microtome 

 well with tissue in center. Tissues must be dry. The sec- 

 tions are to be picked out of the debris. 



4. In gum arabic. Solution thick as possible. Gives in- 

 terstitial as well as internal support. Remove alcohol from 

 tissues by soaking 24 hours in water. Put delicate specimens 

 in gum 6 to 24 hours in paper cone, etc., then place 24 hours 

 in alcohol. Remove paper and imbed in paraffine. 



5. In celloidin. Dissolved in equal parts of alcohol and 

 ether. The dried tissue soaked in alcohol and ether for 3 or 

 4 hours is then put in a thin solution of celloidin for 10 to 12 

 hours, taken out, and, as the ether evaporates and a film is 



.formed, is covered by layers of thicker solution, and kept in 



