274 ANATOMY OF THE DOMESTIC FOWL 



in the foramen through which it passes. The foramen lies between 

 the os petrosum and os occipitale, close to the foramen jugulare, 

 above and to the inside of it. 



The ganglionic root of the vagus communicates with the superior 

 cervical nerve ganglion. The vagus, after coming out of the foramen, 

 takes up branches of the spinal accessory, passes to the superior 

 nerve ganglion, crosses the carotid artery, and then, accompanied 

 by the internal jugular, it connects by a branch with the hypoglossal. 

 It then communicates with the petrosal ganglion, and receives a 

 long branch from the superior cervical ganglion. It then extends 

 along the neck with the jugular vein and often fuses with the sym- 

 pathetic ganglionic plexuses. As it passes, it is interwoven with the 

 glosso-pharyngeus, but each nerve element retains its own individu- 

 ality. Extending down the neck, on entering the thoracic cavity, 

 it lies between the plexus brachialis and the carotid artery. Then 

 it passes below the subclavian artery, and between the bronchial 

 tubes, the aorta pulmonalis, and the subclavian vein. Then ven- 

 trally it rests upon the glands, and the right and the left vagi fuse 

 or unite. From here they radiate down to the stomach in fan shape, 

 and, continuing, they fuse with the sympathetic system. 



The other branches of the vagus are: 



The first branch is the recurrent laryngeus, which supplies the 

 lower end of the bronchial tubes, and the esophagus, then enters 

 above the bronchus near the origin of the subclavian artery as the 

 recurrent cardiacus. 



The second are the recurrent pulmonale which pass into the lungs, 

 each fusing with its fellow from the opposite side, and giving off 

 branches inferior to the vena cava including a branch to the heart. 



The third are the recurrent hepatici which pass through the dia- 

 phragm and are distributed to the liver. 



The Accessorius Spinalis. This is a very small motor nerve 

 (Fig. 62, No. C, 18). It comes out between the dorsal and the ventral 

 root of the third cervical nerve. It lies close to the neck and extends 

 anteriorly, receiving roots from the first and the second cervical 

 nerve. It passes through the occipital foramen into the brain cavity 

 and then enters the ganglion radicis vagi. It passes out of the cranial 

 cavity through the foramen jugulare. It then partly fuses with the 

 vagus and partly, as a fine branch, with the subcutaneous colli. 



The Hypoglossus. The] hypoglossus is a motor nerve (Fig. 62, 

 No. C, 19). It originates anterior to the eleventh pair of cranial 



