258 THB HORSE. 



The Mark. There is a very peculiar hollow extending, when the 

 tooth first comes up, about a half an inch down the temporary and rather 

 deeper down the permanent. This is known as the mark or Infundi- 

 bulum. Up to the age of six there is no use spending time in studying 

 these marks, not because they do not show some indication of age, but 

 because the structural changes detailed above are more reliable. 



After six years have been reached, recourse must be had to the indi- 

 cations given by the marks and other slight, but gradual alterations 

 which take place in the form of the teeth. 



The Construction of the Tooth. The tooth as it originally ap- 

 pears consists of four walls of enamel. The remainder of the tooth con- 

 sists chiefly of dentine, less hard than enamel, and more like ivory. A 

 small quantity of crusta petrosa is also found on the outside. 



This hollow affords lodgement for the debris of the food and only a 

 short time after it makes its appearance it looks black. As the tooth 

 wears down the hollow of course disappears, but the surface of the den- 

 tine immediately below the original hollow, being a somewhat soft ma- 

 terial, has become stained for some distance down. Therefore the black 

 mark remains. With the further wear of the tooth in time this stained 

 portion wears away, and the mark is then out. It is at this age when 

 artificial marks are burned into the tooth to deceive the inexperienced. 



The time required for this mark to wear out varies with the class of 

 food on which the animal has been fed, therefore it is not an £xact guide, 

 yet it may be relied upon to a greater or less degree as an indication 

 of age. 



General Rules as to the Mark. Between three and five years 

 old the marks are very plain in all the permanent incisors. At six the 

 marks are wearing out of the two centre teeth, which came up at three 

 years old. They are plain in the two next, and perfectly fresh in the 

 two corner teeth. 



Seven- Years-Old. At this age the marks from the center teeth 

 have worn away and those in the two next are wearing out, and are dis- 

 tinct and plain only in the corner teeth. 



Bight-Years-Old. Here we find the marks as described have dis- 

 appeared from all but the corner teeth in which they are becoming in- 

 distinct. The faint outlines are to be seen and they will be found to 

 be very elliptical. 



Nine-Years-Old. At this age there are not usually any marks 

 found in the teeth. Faint outlines are still seen being most pronounced 

 in the corner teeth. 



