MAMMALIA. 515 
mastication or rumination is effected by the molar teeth. 
The chewed food is then passed down to the psalterium 
and the abomasum where digestion commences. The 
horse, on the other hand, masticates his food at the time 
of feeding, and there is in this case no rumination or 
“chewing the cud.” The rest of the alimentary canal is 
very similar in both types, the caecum being large and 
the intestine long, characters usually found in herbivorous 
animals. 
Returning to the rest of the skeleton we find that the 
vertebral column is of the same general type, the cervical 
vertebra especially being markedly ofisthocelous. The axis 
vertebra has a crescentic odontoid process, another feature 
in which. the horse and the ox converge, though the more 
primitive forms of each sub-order differ in having simple 
conical odontoid processes. 
The dorso-lumbar vertebrae are ménefeen in number in 
the ox, but ¢wenty-three in the horse. In a similar manner 
the ox has usually twelve to fifteen pairs of ribs, whilst the 
horse has from eighteen to nineteen pairs. The ribs of the 
ox are usually flatter and broader. In both types the front 
dorsal vertebrae bear very long neural spines, to which is 
attached the elastic ligament (Agamentum nuche) running 
forward along the cervical vertebree to the skull and sup- 
porting the weight of the head. 
The difference in the number of dorso-lumbar vertebrae 
is probably due to the shifting of the pelvis further forward 
in the ox than in the horse, in its turn connected with the 
greater proportionate “‘ pushing ” power of the ox. 
Now let us turn to the limbs and limb-girdles. In both 
the same plan prevails. The scapula is elongated and 
narrow, of the cursorial type, and the clavicle is absent ; it 
is not required in animals in which the limbs are not moved 
inwards to the middle line and would indeed be a source of 
danger when, as in jumping, the weight of the body is 
‘thrown on to the fore-limb. The pelvis is of the same 
general type in each, with large ilia fusing not only with the 
primitive sacral vertebree, but with three or four others in 
addition. The limbs have in the cursorial type to perform 
a great uniformity of movement, and by reduction and 
fusion from the pentadactyle type they approximate to the 
