The fifth pair of nerves. 17, The
sixth pair of nerves. 18, 18, The seventh and eighth pair of nerves. 19,
The medulla oblongata, with the crossing of some of its fibres exhibited.
20, The ninth pair of nerves. 21, The tenth pair of nerves, 22, The
eleventh pair of nerves. 23, The twelfth pair of nerves.]

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Describe this portion of the brain. Explain fig. 122.

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737. The MEDULLA OBLONGATA, or that portion of the spinal cord which
is within the skull, consists of three pairs of bodies, (_cor'pus
py-ram-i-da'le_, _res-ti-for'me_, and _ol-i-va're_,) united in a
single bulb.

[Illustration: Fig. 123. The base of the skull and the openings through
which the cranial nerves pass. 1, 1, The first pair of nerves. 2, 2, The
cribriform plate of the ethmoid bone through which this nerve passes. 3,
3, The second pair of nerves. 4, 4, The optic foramen in the sphenoid
bone; through which passes the second pair of nerves. 5, 5, The
sphenoidal fissure. 6, 6, The third pair of nerves. 7, 7, The fifth pair
of nerves. 8, 8, The ophthalmic branch of the fifth nerve. The third, the
ophthalmic branch of the fifth and the sixth nerve pass from the brain
through the sphenoidal fissure to the eye. 9, 9, The superior maxillary
branch of the fifth nerve. 10, 10, The foramen rotundum, (round opening,)
through which the nerve 9, 9, passes to the upper jaw. 11, 11, The
inferior maxillary branch of the fifth pair. 12, 12, The foramen ovale,
(oval opening,) through which the nerve 11, 11, passes to the lower jaw.
13, 13, The sixth pair of nerves. 14, 14, The seventh and eighth pair of
nerves. 15, 15, The opening in the temporal bone, through which the
seventh and eighth nerves pass to the face and ear. 16, 16, The ninth
pair of nerves. 17, The tenth pair of nerves. 18, 18, The eleventh pair
of nerves. 19, 19, The foramen lacerum (rough opening.) The ninth, tenth,
and eleventh nerves pass from the brain through this opening. 20, The
spinal cord. 21, The foramen spinalis, through which the spinal cord
passes. 22, 22, The position of the anterior lobe of the brain. 23, 23,
The middle lobe. 24, 24, The posterior lobe. 25, 25, A section of the
skull-bones.]

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737. Describe the medulla oblongata. Explain fig. 123.

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738. The DURA MATER is a firm, fibrous membrane, which is exposed on
the removal of a section of the skull-bones. This lines