492 



THE HORSE'S POSITION IN THE ANIMAL WORLD 



The most interesting point, liowever, remarks M. D. J. Cunningham, 

 in connection with its structure is that it bears its history on its face. 

 Almost invariably two thin streaks of striated muscular fibre are to be 

 found on its superficial surface, leading down to the two inferior divisions. 

 On examining its deep surface two very distinct strands of pink, fieshy 

 tissue are always observed extending throughout the entire length of 

 the ligament. These consist in each case of short oblique striated fibres, 

 and are presumed to represent the two heads of the muscle called the 



flexor brevis, not yet converted 

 into fibrous tissue. It is hardly 

 necessary to suggest that mus- 

 cular fibre in such a form and 

 position, and with such sur- 

 roundings, cannot possess any 

 functional value, that is, does 

 not serve any really useful end. 

 Indeed, it can only be looked 

 upon as a vestigial tissue which 

 is slowly passing away. 



The Head. — Proceeding 

 from the consideration of the 

 bones of the limbs we will 

 next give particular attention 

 to the head, mainly on account 

 of the teeth. These, although 

 in the popular view they are 

 looked upon merely as organs 

 for masticating food, and for 

 this purpose are divided into 

 front and back teeth or in- 

 cisors and molars, do really possess very special features, by the aid of 

 which the naturalist is enabled to determine the family or order to which 

 animals belong. 



The exploit of the palaeontologist in constructing the model of an 

 extinct animal from a single fossil bone or tooth is often aceejjted as a 

 trick of sleight-of-hand, more calculated to amuse than to instruct, but 

 when all the facts are known there is really nothing very wonderful 

 in the procedure. Anyone, for example, who is familiar with the form 

 of the teeth of the shark could hardly make a mistake in their identifi- 

 cation, and if a fossilized tooth of a shark were placed in his hand he 

 would at once, in imagination, construct the animal to which the tooth 



Fig. 660. — Side View of Skull of Man, with the bone 

 removed so as to show the whole of the teeth 



z, Zygomatic arch ; ii, nasal bone; o, orbit; t, temporal fossa; 

 oc, occipital condyle; e, external auditory opening; ff, clenoid 

 fossa for articulation of the lower jaw ; co, coronoid process of 

 lower jaw; i^ and i", incisor teeth; c, canine; pvti and pm^, 

 premolar teeth ; m' in' m', the three molar teeth. 



