6o6 



TEXT-BOOK OF PHYSIOLOGY. 



TWELFTH NERVE. THE HYPOGLOSSAL. 



The twelfth cranial nerve, the hypoglossal, consists of peripherally 

 coursing nerve-fibers which serve to connect the nerve-cells from which they 

 arise with the musculature of the tongue. 



Origin. The axons composing the hypoglossal nerve arise from a collec- 

 tion of nerve-cells situated beneath the floor of the fourth ventricle. This 

 nucleus is elongated and extends from the medullary striae downward as far 

 as the lower border of the olivary body. It is located ventro-laterally to the 



FIG. 282. DISTRIBUTION OF THE HYPOGLOSSAL NERVE. i. Root of the fifth nerve. 2. 

 Ganglion of Gasser. 3, 4, 5, 6, 7, 9, 10, 12. Branches and anastomoses of the fifth nerve, u. 

 Submaxillary ganglion. 13. Anterior belly of the digastric muscle. 14. Section of the mylo- 

 hyoid muscle. 15. GLOSSO-PHARYNGEAL NERVE. 16. Ganglion of Andersch. 17,18. Branches 

 of the glosso-pharyngeal nerve. 19, 19. Pneumogastric. 20,21. Ganglia of the pneumogastric. 

 22, 22. Superior laryngeal branch of the pneumogastric. 23. Spinal accessory nerve. 24. 

 Sublingual nerve. 25. Descendens noni. 26. Thyro-hyoid branch. 27. Terminal branches. 

 28. Two branches one to the genio-hyo-glossus and the other to the genio-hyoid muscle. 

 (Sappey.) 



spinal canal. After leaving the cells of the nucleus the axons pass forward 

 and outward toward the surface of the medulla, from which they emerge in 

 ten or twelve small bundles or filaments in the groove between the olivary 

 body and the anterior pyramid. Beyond this point they unite to form 

 a common trunk. 



Distribution. The common trunk thus formed passes out of the cranial 

 cavity through the anterior condyloid foramen. In its course it receives 



