86 A MANUAL OF DENTAL ANATOMY. 



of ordinary hard dentine, surmounted by enamel tips. In 

 this part of the tooth the dentinal tubes are numerous, and 

 regular in their disposition, radiating out from the axial pulp 

 chamber. 



Lower down in the teeth the dentinal tubes become less 

 numerous, and at the same time much larger looped canals 

 make their appearance, and as these become more numerous 

 and regular so do the dentinal tubes become less so. These 

 larger tubes contain blood-vessels, and red blood circulates 

 through them during the life of the tooth. 



We may suppose that the nutrition of the dentine maybe 



FIG. 45 ( 1 ). 



provided for either by protoplasm carried for a long distance 

 from the pulp by the dentinal tubes, or by blood circulating 

 through the larger vascular channels, but that both are not 

 required, and so do not exist together. 



And whilst the teeth of the Manatee, the Tapir, and of 



f 1 ) Tooth of Ostracion. a, Enamel ; I, Capillary channels ; c, Axial 

 pulp chamber. 



