50 

 further retracted, and this gives to these organs an 

 irregular oblong figure, which is very different from 

 the semi-circular shape of the milk teeth. The in- 

 cisors, however, are not of equal length in all horses, 

 and in some the gum may be so prominent as to give 

 the permanent somewhat the appearance of a tem- 

 porary incisor ; other indications, however, even then, 

 enable the different nature of each to be with cer- 

 tainty distinguished. The enamel is only partially 

 exposed in the horse tooth ; the shaded portion of 

 Figure 1, in the preceding wood-cut, denotes the 

 extent to which it is generally covered during the 

 period of dentition ; and when the teeth first appear, 

 the enamel is wholly concealed by a covering of 

 crusta petrosa. That covering is never entirely re- 

 moved — a small portion of it, even in the oldest 

 mouths, is seen near to the gums. It looks like an 

 accumulation of tartar, and is most conspicuous in 

 the tooth that has been newly cut. The presence or 

 absence of this substance, therefore, should be noted, 

 and moreover, the enamel surface should be further 

 inspected. The numerous channels that give so 

 peculiar a fluted appearance to the milk tooth, are 

 not to be seen upon that of a permanent description ; 



