of the Animals of the Farm. 
423 
forming an opinion of the age ; but no exact estimate can be 
based on such evidence. The five-jear-old ox will show 
a considerable amount of worn surface in the central, middle, 
and lateral incisors, and the cutting edge of the corner teeth 
will be marked by a line of wear ; but no one would attempt to 
Fig. 33. — Incisors of Ox at three years and three months. 
determine whether or not an animal were under or above the 
age of five, and as the years increase, the difficulty of judging 
the age by the appearance of the teeth is not diminished. 
The teeth become narrower and more widely separated from 
each other year by year, but the changes are not sufficiently 
well marked to enable the examiner to accept them as 
reliable evidence of age. 
The Teeth of the Sheep. 
The terms which are applied to the teeth of the ox for the 
purpose of description may be used in regard to the teeth of the 
sheep. Eight incisors, central, lateral, middle, and corner teeth, 
are found in front of the lower jaw only, the corresponding part 
of the upper jaw being provided with an elastic pad, as in the 
