16 VETERINARY DENTAL SURGERY. 



True teeth consist of three tissues which are char- 

 acterized by different degrees of density. These are 

 the Dentine, Enamel and Cement or Crusta-petrosa. 



Dentine is a hard whitish yellow substance, form- 

 ing the greater portion of a tooth, and consists of an 

 organized animal basis disposed in the form of very 

 minute tubes and cells, and of earthy particles. 

 These earthy particles have a twofold arrangement, 

 being either blended with the animal matter of the 

 interspaces and parieties of the tubes and cells, or 

 contained in a minutely and irregular granular state 

 in their cavities. The density is due to the propor- 

 tion of earthy material, 72 per cent being earthy 

 matter and 28 per cent animal matter. The tubes 

 and cells also contains a colorless fluid, "liquor san- 

 guinis" which furnishes nutrition to this portion of 

 the tooth. Dentine is non-vascular in the higher 

 types of vertebrates, but in some of the lower forms 

 the teeth are traversed by blood vessels. Fig. 2 

 shows a section through a molar tooth and illustrates 

 the tubuli of the dentine. 



The enamel is a thin layer of very dense tissue 

 which covers the crown portion of the dentine, and 

 and in some animals (the horse and Ruminantia) it 

 dips into the table surface of the tooth to a great 

 depth. It is very hard and white, taking a high 

 polish during the process of mastication. It consists 

 of 96.5 per cent of earthy matter and 3.5 per cent of 



