398 



DIGESTIVE SYSTEM OF THE HORSE 



Infundihulum 



Central enamel 

 Dentine 

 Peripheral 

 eiiamel 



Cement 



alveolus, so that the masticatory surfaces of the first and second lower incisors 



are at first oval, with the long diameter transverse; 

 later — at about fourteen years usually for the first 

 lower incisors — they are triangular, with the base 

 at the labial edge. At the same time the infundih- 

 ulum or "cup" becomes smaller, approaches the 

 Ungual border, and finally disappears; it remains 

 longer on the upper incisors, as it is -deeper in 

 them. Another marked feature in old age is the 

 progressive approach to a horizontal direction as 

 seen in profile;- at the same time the exposed 

 crowns of the teeth become parallel and finally 

 convergent. 



Canine Teeth. — These are four in number in the 

 male; in the mare they are usually absent or rudi- 

 mentary. ^ They interrupt the interdental space, 

 dividing it into unequal parts. The upper canine 



Peripheral enamel Cement 

 Dentine ~ 

 Central enamel- 

 Cement-, 



Fig. 338. — Longitudinal Section of 



Lower Incisor Tooth of Hohsb. 



C, Pulp cavity. Cement is shown in the 



infundihulum, but is not marked. 



Fig. 339.- 



-Cross-section of Lc 



/, Infundihulum. 



or Tooth of Horse, 



is situated at the junction of the premaxilla and the maxilla; the lower canine is 

 nearer the corner incisor. The canines are simple teeth, smaller than the incisors, 



Fig. 340. — Loweh Incisoe aot) Canine Teeth oe Fig. 341. — Upper Incisor and Canine Teeth of 



Horse, Five Years Old. Horse, Five Years Old. 



The lingual border of the third upper incisor is unworn. /', I^, I', Incisor; C, canine. 



and are curved with the concavity directed backward. The exposed crown in the 



1 It is interesting to notice that vestigial canines are not at all uncommon in mares, espe- 

 cially in the lower jaw. They are very small, and do not usually erupt; their presence is indi- 

 cated in the latter case by a prominence of the gum. This is in conformity with the fact that 

 they were present in both sexes in Eocene and Miocene ancestors of existing equidae. 



