as indicative of the Age of the Animal. 
321 
ance of the first permanent molars. Most of our authorities 
concur in sajing that these teeth arc cut when the animal is about 
a year old. These statements, however, aie far from being- correct, 
for these teeth are put up when the calf is six months old. 
In fi". 23, I have represented a side view of one half of the 
lower jaw of a calf, reduced one fourth from its natural size ; 
and it will be seen that the fourth Permanent Molar, marked 
4 p. M., is in its place. I have found, as a rule, that this molar 
in the lower jaw is usually a little more forward than its fellow 
in the upper, and now and then appears even before the sixth 
month. This tooth, it will be remembered, is of less length than 
the third molar, as measured from front to bac k, but wider from 
side to side, gaining thereby a more proportionate outline. In 
about three months the fourth molars attain an equal height with 
the others. 
The next important stage in dentition is the cutting of the fifth 
molar in situation, the second permanent. This takes place at 
fifteen months ; but as in the interim well marked changes have 
come on in the temporary incisors, it is necessary to direct atten- 
tion in the first instance to these. 
From six to nine or ten months, the edges of the incisors, which 
at the former date were rather blunted, have been gradually giving 
way to attrition : this perhaps would be scarcely recognised in an 
ordinai-y examination. After the latter period, however, it becomes 
more and more apparent, and when the animal is a year old, the 
four centrally-placed teeth, in particular, Avill be worn rather flat on 
their crowns. These teeth also are now beginning to show spaces 
between their fangs. 
These changes are re- 
gulated partly by the 
system of management 
the young animal has 
received, and the kind 
of food on which it 
has been kept — partly 
by the natural width of 
the lower jaw. If the 
food has been coarse 
and the jaw be a wide 
one, the incisors will 
be more flat and the 
distance between them 
greater than otherwise. 
In the preceding illustration, fig. 24, is represented the more 
* Fig. 24. Front part of tlie lower jaw of a year-old ox, showing the wear of 
the incisors and their separation somewhat from each other. Natural size. 
Fig. 24.* 
