EQUIDsE 397 



quadrate, except the first and last, which are nearly triangular. 

 The lower teeth are much narrower than the upper. 



The milk dentition consists of i f , c $, m f = 24, the canines 

 and first or rudimentary premolars having apparently no pre- 

 decessors. In form and structure they much resemble the 

 permanent teeth, having the same characteristic enamel -foldings. 

 Their eruption commences a few days after birth, and is complete 

 before the end of the first year, the upper teeth usually appear- 

 ing somewhat earlier than those of the lower jaw. The first 

 teeth to appear are the first and second milk-molars (about 

 five days), then the central incisor (from seven to ten days) ; this 

 is followed by the second incisor (at one month), then by the third 

 molar, and finally by the third incisor. Of the permanent teeth the 

 first true molar appears a little after the end of the first year, 

 followed by the second molar before the end of the second year. At 

 about two and a half years the first premolar replaces its predecessor. 

 Between two and a half and three years the first incisor appears. 

 At three years the second and third premolars and the third true 

 molar have appeared ; at from three and a half to four years the 

 second incisor ; at four to four and a half years the canine ; and, 

 finally, at five years the third incisor, completing the permanent 

 dentition. Up to this period the age of the horse is clearly shown 

 by the state of the dentition, and for some time longer indications 

 can be obtained from the wear of the incisor teeth, though this 

 depends to a certain extent upon the hardness of the food or other 

 accidental circumstances. As a general rule, the depression caused 

 by the infolding of the surface of the incisor (the " mark ") is 

 obliterated in the first or central incisor at six years, in the second 

 at seven years, and in the third at eight years. In the upper teeth, 

 as the depressions are deeper, this obliteration does not take place 

 until about two years later. After this period no certain indica- 

 tions can be obtained of the age of the horse from the teeth. 



Digestive Organs. The lips are flexible and prehensile. The. 

 membrane that lines them and the cheeks is quite smooth. The 

 palate is long and narrow; its mucous surface has seventeen pairs 

 of not very sharply defined oblique ridges, extending as far back as 

 the last molar tooth, beyond which the velum palati extends for 

 about 3 inches, having a soft corrugated surface, and ending 

 posteriorly in an arched border without uvula. This embraces the 

 base of the epiglottis, and shuts off all communication between 

 the cavity of the mouth and the nasal passages, respiration 

 being, under ordinary circumstances, carried on exclusively 

 through the nostrils. Between the mucous membrane and 

 the bone of the hard palate is a dense vascular and nervous 

 plexus. The membrane lining the fauces is soft and corrugated. 

 An elongated raised glandular mass, 3 inches long and 1 inch from 



