322 
On the Teeth of the Ox, Sheep, and Pig, 
usual state of the incisors at a year old. 
Fig. 25.* 
The engraving is of na- 
tural size, that the pecu- 
liarities may be the better 
recognised. 
From one year we pass 
to fifteen months, when, 
as before stated, the fifth 
molar tooth is put up. 
This tooth does not es- 
sentially differ from the 
fourth in its shape or 
dimensions. Its cut- 
ting, however, at fifteen 
months, when the incisors 
offer no satisfactory evi- 
dence of precise age, is 
a jioint of some utility 
to an investigator. For 
the periods of appearance 
of the permanent molars 
are pretty uniform. The 
fourth, as we have seen, is 
cut at six, and the fifth at 
fifteen months : the sixth 
follows at two years — an 
interval of nine months 
elapsing between each. 
Tills gradation is easily 
remembered. Fig. 25 
shows the fifth molar in 
the act of being cut. The 
engraving represents one- 
half of the lower jaAV at 
fifteen months old, re- 
duced one-third from its 
natural size ; this tooth 
being marked 5 p. m., to 
distinguish it from the 
fourth molar, 4 p. m. Like 
the fourth molar, t'lis 
tooth also acquires its full 
height in the jaw about 
three months from the 
time of its cutting. 
* Fig. 25. One half of the lower jaw of an ox 15 months old, two-thirds the 
natural size, representing the fifth molar as being cut. The fourth in situation 
(first permanent) is marked 4 P. M. ; the fifth, 5 P. si. 
