Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/26

12 petrosal and occipital bones. This foramen transmits the ninth (glossopharyngeal), tenth (vagus), and eleventh (accessory) cranial nerves. The carotid foramen is anterior to the jugular foramen, between the tympanic bulla and the basioccipital bone. Near the posterior ends of the pterygoid processes is a pair of foramina which communicate with one another by a horizontal space in the basisphenoid bone. A large oval foramen lies immediately anterior to the one just mentioned. Note the communication of this oval foramen with the superior orbital fissure. Ventral to the foramen ovale another large oval foramen perforates the posterior part of the lateral pterygoid process. Note the two slits in the cranium, dorsal and posterior to the choana, communicating with the anterior lacerated foramen.

The prepalatine foramina are two conspicuous slits on the roof of the mouth in the region of the diastema. They are surrounded by the maxillary and premaxillary bones. The postpalatine foramina perforate the roof of the mouth near the lateral margin of each palatine bone. A bristle inserted through the foramen will show its communication with the groove on the floor of the orbito-temporal fossa.

Exercise III. Draw and label the ventral view of the cranium.

Interior of the cranium. Bisect the skull vertically in a plane slightly at one side of the sagittal plane. Use a sharp bone saw with small teeth. Care should be exercised to injure the bones as little as possible.

Two cavities will be observed, the cranial cavity for the brain, and the nasal cavity. The cranial cavity is subdivided further into the cerebellar, cerebral, and olfactory fossae.

The cerebellar fossa holds the cerebellum. It occupies the posterior part of the cranium and is partially sepa-