66 EXAMINATION OF HORSES AS TO SOUNDNESS 



outside of the enamel is covered by a very thin 

 calcified substance termed the cuticle of the 

 enamel. 



Surrounding that portion of the dentine which 

 is situated beneath the level of the gum is the 

 crusta petrosa, or cement, which is composed of 

 true bone. 



At the neck the crusta petrosa and enamel 

 come in contact, the enamel increasing in thickness 

 towards the crown of the tooth, and the crusta 

 petrosa towards the end or root of the fang. 



At the superior part or table of an incisor 

 tooth is noticed a cavity of variable depth, called 

 the infundibulum. The infundibula are deeper 

 in the permanent teeth than in the temporary, 

 are greater in the upper jaws than in the lower, 

 are present in the superior or upper molars, but 

 not in the inferior. The inferior molars have 

 no infundibula, but only grooves and fissures. 



In structure dentine, which closely resembles 

 bone in its chemical composition, is seen under 

 the microscope to be finely channelled by a large 

 number of delicate tubes, which communicate 

 with the pulp cavity by their inner ends, and by 



