66 



THE HORSE 



traces of the gland can be found ; for it is present in a 

 most rudimentary condition, without showing any im- 

 pression on the surface of the bone below, in several of 

 the existing Bovidce, the sheep for instance. In this 

 animal, its place in the economy of life is supplied by 

 the curious little bottle-like glandular pouches placed 

 between the toes. 



Another easily-recognised distinction between the 

 hipparion and all modern horses is seen in the structure 



Fig. 10. — Section of upper molar tooth of hipparion, from 

 the Red Crag of Suffolk. a.i, anterior internal column 

 completely isolated from the main mass of dentine ; pA, 

 posterior internal column. The uncoloured portion is 

 the dentine, the shaded part the cement, and the black 

 line separating these two the enamel. Compare with 

 fig. 21, c y p. 125. 



of the upper molar teeth. The anterior inner cusp of the 

 primitive form (fig 10, a. i) constitutes a distinct column 

 instead of being, as in the horse, united for its whole 

 length with the rest of the tooth. The foldings of the 

 enamel are also developed to a remarkable extent of 

 complexity. These characters cannot be clearly under- 

 stood until the details of the structure of the teeth, 



