330 MANIPULATION. 



that used for iron and brass; even this will often become 

 blunt before the cutting is completed. It will be almost 

 vain to indulge in the hope of making more than two longi- 

 tudinal sections of one tooth; this can only be effected by 

 cutting it down through the middle, and after cementing the 

 cut surfaces to a plate of glass, to reduce them to the proper 

 degree of thinness by the file, and finish them on the hones. 

 The lapidary's wheel wiU be found much more useful for teeth 

 than for bone, as a wheel charged with diamond dust will 

 speedily cut through a thick layer of the hardest enamel. 

 The operation of laying sections of teeth in the thick balsam 

 should be carefully performed, as the enamel very readily 

 separates from the dentine or ivory; the grinding and polishing 

 should also be carried on with care to prevent the separation. 

 The sections, like those of bone, should be made in two 

 directions, one transverse, and the other longitudinal, and if 

 the structure of the enamel require to be examined, an oblique 

 section will be found very instructive, although very difficult 

 to make. 



To Mount Sections of Teeth. — These may be mounted in 

 the same way as the sections of bone ; an examination by the 

 microscope wiU serve to determine whether any particular 

 specimen should be placed either in fluid or balsam, or be 

 preserved dry ; the latter plan wiU, however, be found on the 

 whole to be the most satisfactory, but in this case the section 

 should be well polished. Dark coloured fossil teeth wiU be 

 well exhibited in balsam, and may even be boiled in it if 

 necessary, as the tubes of the dentine are in most cases filled 

 with earthy matter. 



