The Teeth

The dental formula of the ox is:

( 0 0 3 3 )

2 ( I

C

P

M

) = 32

( 4 0 3 3 )

The incisors are absent from the upper jaw. There are eight incisors in the lower jaw, arranged in a somewhat fan-like manner. They are simple teeth, without infundibulum. The crown is white, short, and shovel-shaped. The root is rounded, and is embedded in the jaw in such a manner as to allow a considerable degree of movement. There is a distinct neck. In addition to the simple numerical designation, the following terms are commonly applied to the individual teeth: pinchers or central, first intermediate, second intermediate, and corner incisors. It is probable that the latter are much modified canines. The incisors of the ox do not advance out of the alveoli, as is the case in the horse; in old age, however, the gum retracts so that the roots are partly exposed and may come into wear.

The deciduous incisors differ from the permanent set chiefly in being much smaller. The crowns are narrower and diverge more.

The canines are absent (unless the fourth incisors be considered to represent them).

The cheek teeth (Fig. ) resemble those of the horse in number and general arrangement. They are, however, smaller, and also differ in the fact that they progressively increase in size from before backward. This feature is so marked that the first tooth is quite small, and the space occupied by the first three (i. e., the premolars) is only about one-half of that required for the posterior three (i. e., the true molars). The enamel folds stand out even more prominently in relief on the masticatory surface than in the horse. The occurrence of wolf-teeth is rare.

The formula of the deciduous teeth is:

( 0 0 3 )

2 ( Di

Dc

Dp

) = 20

( 4 0 3 )

TABLE OF AVERAGE PERIODS OF ERUPTION OF THE TEETH IN THE OX

Teeth Eruption

A. Temporary:

First incisor (Di 1) Birth to 3 weeks.

Second incisor (Di 2)

Third incisor (Di 3)

Fourth incisor (Di 4)

First cheek tooth (Dp 1) Birth to 3 weeks.

Second cheek tooth (Dp 2) Birth to few days.

Third cheek tooth (Dp 3)

B. Permanent:

First incisor (I1) 1½ to 2 years.

Second incisor (I2) 2 to 2½ years.

Third incisor (I3) 3 years.

Fourth incisor (I4) 3½ to 4 years.

First cheek tooth (P1) 2 to 2½ years.

Second cheek tooth (P2) 1½ to 2½ years.

Third cheek tooth (P3) 2½ to 3 years.

Fourth cheek tooth (M1) 5 to 6 months.

Fifth cheek tooth (M2) 1 to 1½ years.

Sixth cheek tooth (M3). 2 to 2½ years.

The eruption of the permanent teeth is subject to great variation. The above figures are the average of observations of improved breeds under favorable conditions.