CHAPTER XI 

 TOOTH, BONE, AND OTHER HARD OBJECTS 



Sectioning Decalcified Tooth. 1. Kill a cat and remove the 

 lower jaw (p. 53). With a fine saw cut out about a quarter of an 

 inch of the bone bearing a tooth (e. g., canine), remove as much 

 of the surrounding tissue as possible and place the object in 

 Erlicki's fluid for several days. Transfer to nitric acid decalcify- 

 ing fluid (reagent 11, chap. i). Use a relatively large quantity 

 of the fluid and change it each day until the tooth is decalcified 

 (2 to 6 days). It is sufficiently soft to cut when a needle can be 

 thrust into it easily. 



2. Wash it in repeated changes of 70 per cent, alcohol until 

 all trace of the acid is removed (about 2 days) as shown by 

 litmus paper. 



3. Transfer the object through 50 and 35 per cent, alcohol 

 successively to running water and wash for 24 hours. 



4. Cut sections by means of the freezing microtome as directed 

 under that method (chap. viii). If a freezing microtome is not 

 available use the celloidin method. 



5. After dissolving out all of the gum from the sections in 

 distilled water, immerse them for half an hour in picro-carmine, 

 then remove one or two of the best (through the center of the 

 tooth) to a slide, drain off the excess of stain and add a few drops 

 of melted glycerin-jelly. Cover with a circular cover-glass. 



6. When the jelly has hardened, seal the cover with gold size 

 and when this is dry, add a thin coat of Bell's cement (see 

 chap, xiii, ii, A, 6). 



7. Stain other sections in 1 per cent, osmic acid for 24 hours 

 and mount in glycerin- jelly as above or dehydrate and mount in 

 balsam. 



Sectioning Decalcified Bone. Saw out a short piece from the 

 femur of a cat (p. 53). Prepare transverse sections by decalcify - 



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