THE DIGESTIVE SYSTEM 



71 



Infundibulum 



Central enamel 

 Dentin 



Peripheral 

 enamel 



Cement 



In this formula the letters indicate the kinds of teeth, and the 

 figures above and below the line give the number of teeth 

 of one side in the upper and lower jaw respectively. 



The dental formula for the horse varies from the fact that the 

 wolf teeth, which are vestigial, may or may not be present. These 



teeth are classified as upper pre- 

 molars,, but in some subjects occur 

 in the lower jaw. There is still a 

 controversy as to whether they 

 belong to the permanent or tem- 

 porary set. The presence of wolf 

 teeth does not cause eye disease 

 or weakness, as is popularly 

 supposed. 



Anatomically, an incisor tooth 

 is divided into the crown, neck, 

 root, infundibulum, and cup. The 

 crown refers to the projecting por- 

 tion or that part that is visible. 

 The neck is the part covered with 



Peripheral enamel Cement 

 Dentin . 

 Central enamel 

 Cement 



Fig. 17. — Longitudinal section 

 of lower incisor tooth of horse: C, 

 Pulp cavity. Cement is shown 

 in the infundibulum, but is not 

 marked. (Sisson, Anatomy of 

 Domestic Animals.) 



Fig. 18. — Cross-section of lower incisor 

 tooth of horse: I, Infundibulum. (Sisson, 

 Anatomy of Domestic Animals.) 



the gum. The root is the portion that is embedded in the jaw 

 bone. The infundibulum is the cavity on the table surface 

 produced by the infolding of the enamel. The cup refers to 

 the unfilled portion of the infundibulum of an incisor tooth. 

 Teeth are composed of dentin, which is capped with enamel and 

 encrusted over the remaining portion with cement (Figs. 17, 18). 

 The dentin is dense in consistency, yellowish-white in color, and 

 forms the bulk of most teeth. It surrounds the pulp cavity. 



Digitized by Microsoft® 



