Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/38

24 behind the body. Three processes are attached to its posterior end. The coronoid process projects dorsally into the orbito-temporal fossa. Just behind this is the condyloid process, bearing an elongated rounded knob which articulates with the mandibular fossa of the squamosal bone. These articular surfaces in the rodent permit anteroposterior motion of the jaw. The angular process is directed posteriorly. The anterior mandibular incisure is a pronounced depression separating the coronoid from the condyloid process. The posterior mandibular incisure likewise separates the condyloid and angular processes. The mandibular foramen lies at the base of the condyloid process. The mental foramen lies ventroanteriorly to the molar teeth. Other foramina occur on the surface of the mandible. A ridge extends on the lateral surface of the mandible from the mental foramen backward to the border of the angular process. The medial surface of this process is concave. The incisor tooth of the lower jaw, like that of the upper, is sickle-shaped, and inserted in a large dental alveolus which extends caudally, ventral to the molar teeth, nearly to the base of the condyloid process. The mandible is largely a membrane bone.

The hyoid is a u-shaped bone at the base of the tongue composed of a slender transverse body and two pairs of horns (cornua), one pair extending anteriorly, the other pair posteriorly.

Exercise IV. Make a labeled sketch of each of the bones of the head.

The vertebral column, or backbone, is the second division of the axial skeleton. It is a linear series of numerous