30 PREPARING SECTIONS OF TEETH. 



30 per cent, spirit, change to 50 per cent., and again after a similar 

 period to 70 per cent. To remove the black sublimate precipitate, 

 place the teeth for twelve hours in 90 per cent, spirit, to which 

 1*5 to 2 per cent, tincture of iodine has been added. The 

 iodine is afterwards removed by immersion in absolute alcohol 

 until the teeth become white. 



To Stain in Borax Carmine, either an alcoholic or aqueous 

 solution gives the best results. Remove the teeth from absolute 

 alcohol to running water for fifteen to thirty minutes, and then 

 place in the stain. In the watery solution of borax carmine they 

 must remain one or two days, and in the spirituous two or three 

 days. Transfer to acidulated spirit (70 per cent, spirit, 100 parts ; 

 muriatic acid, i part), in which they may remain ; the watery ones 

 stained require at least twelve, and the alcohol stained ones 

 twenty-four to thirty-six hours. This done, immerse for about 

 fifteen minutes in 90 per cent, spirit and then for half-an-hour in 

 absolute alcohol ; after which they are to be transferred to some 

 ethereal oil for twelve or more hours ; then quickly wash the ethe- 

 real oil off the objects with pure xylol. They are then to be 

 passed into a solution of balsam in chloroform. 



The Balsam is prepared by drying in a water-bath heated gra- 

 dually up to 90 deg. for eight hours or more until, when cold, the 

 mass will crack like glass on being punctured. Of this balsam so 

 much is added to the chloroform as to make a thin solution, in 

 which, as stated above, the teeth must lie for twenty-four hours. 

 Then add as much balsam as the solution will dissolve. When no 

 more balsam will dissolve, the teeth and a sufficiency of the 

 balsam are poured into a vessel and heated up to 90 deg. in a 

 water-bath until the mass, when cold, shall be as hard as glass. 

 Let the balsam set ; pick out the teeth carefully, place in a vice, 

 and thin discs are cut from them with a fret-saw, water being 

 trickled over them the while. Mount sections in chloroform 

 balsam. 



Teeth to show Odontoblasts in situ.— Take the jaw, preferably 

 the lower jaw, of an embryonic mammal such as a kitten or puppy, 

 and while still fresh carefully strip off the tissues covering it, except 

 the oral epithelium and flange of gum, and place in the usual 

 MuUer solution, twenty to thirty times in volume greater than the 



