Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/122

108 through the anterior lacerated foramen and innervate the external rectus muscles of the eyes.

The seventh cranial nerves (facial) emerge from the side of the medulla behind the fifth, and leave the cranium through the facial canals just behind the external auditory meatuses. They send branches to the lateral surfaces of the muscles of mastication, where they may easily be seen when the skin is removed from the head.

The eighth nerves (acoustic) arise from the medulla oblongata behind the seventh, penetrate the auditory capsules, and reach the inner ears.

The ninth nerves (glossopharyngeal) arise from the medulla oblongata close to the tenth. Leaving the skull by the posterior lacerated foramen, they send branches to the pharynx and tongue. They are anterior to, and deeper than, the twelfth nerves, and lie close to the skull.

The tenth nerves (vagus or pneumogastric) arise from the side of the medulla oblongata posterior to the eighth, and leave the cranium through the posterior lacerated foramen. Shortly after emerging they give off the superior laryngeal nerves to the larynx, then proceed back to the thoracic cavity along the common carotid artery. The recurrent laryngeal nerve is given off near the entrance of the vagus into the thorax. Trace it forward, on both sides, along the esophagus to the larynx. On the right it turns forward from the vagus dorsal to the subclavian artery, on the left side dorsal to the aortic arch. The tenth nerves in the thorax lie dorsal to the heart and lungs, which they are said to innervate. Passing backward along the esophagus, they penetrate the diaphragm, then innervate the stomach.

The eleventh nerves (accessory) arise from the anterior region of the spinal cord, and from the medulla enter the skull through the foramen magnum, unite with the vagus