TEETH. 8 1 



cells. The pulp cavity is open at the root of the 

 tooth for the admission of vessels and nerves. Sur- 

 rounding the root of the tooth is a thin layer of 

 bone called cement. At the crown of the tooth the 

 dentine is completely covered by a layer, of varying 

 thickness, of an extremely hard substance called 

 enamel. The enamel consists of a series of closely 

 packed, small, wavy or undulating prisms, placed 

 edgewise upon the surface of the dentine, and cov- 

 ered, over the free surface of the tooth, by a hard, 

 tough, structureless membrane, called the enamel 

 cuticle. 



TECHNIQUE. 



Hard Teeth. To study the hard parts of teeth, thin 

 sections of a macerated and dried tooth should be ground 

 down by the method described when we were studying 

 hard bone, and mounted, with the same precaution, in 

 hard Canada balsam. 



Decalcified Teeth. The soft parts of teeth may be 

 studied in sections from teeth which have been decalci- 

 fied with picric acid. The tooth should be broken 

 across, so as to expose the pulp cavity and hasten the 

 action of the solvent. Sections are stained with haema- 

 toxylin and eosin, and mounted in glycerin. 



