72 PRACTICAL ANATOMY. 



(i) The carotid artery ; (2) the internal jugular vein ; (3) the vagus nerve ; 

 (4) the cervical sympathetic, behind the carotid sheath ; (5) the recurrent 

 laryngeal nerve ; (6) the apex of the parietal pleura. 



26. Name tlie brandies of the liypoglossal nerve. 



(i) A communicating branch to the cervical plexus to form the ansa hypo- 

 glossal loop. (2) Muscular branches to the sterno-hyoid, omo-hyoid, sterno- 

 thyroid, thyro-hyoid, stylo-glossus, hyo-glossus, and genio-hyo-glossus. 



27. Explain the digastric muscle. 



It has an anterior belly, a posterior belly, an intermediary tendon. The 

 attachments are the digastric groove of the temporal bone and the digastric fossa 

 of the mandible, the body of the hyoid bone. The action of the muscle depends 

 on its fixed point. When the depressor muscles of the hyoid bone fix this bone, 

 then the digastric depresses the mandible. In the act of swallowing, the hyoid 

 bone is elevated by the digastric and its probably dismembered synergist, the 

 stylo-hyoid. The seventh nerve supplies the posterior belly ; the mylo-hyoid 

 branch of the inferior dental of the fifth nerve, the anterior belly of the digastric. 



28. What important nerve did you find on tlic outer part of the hyo-glossus 

 muscle ? 



The hypoglossal, the motor nerve of the tongue. The lingual artery passes 

 behind the muscle. 



29. Explain fully the liyo-glossus muscle. 



The action of the muscle is to make the back of the tongue convex, and to 

 retract the tongue. The origin is from the outer third of the anterior part of 

 the body of the hyoid bone and from both the greater and lesser cornua. The 

 muscle is inserted into the side of the tongue. 



30. Name the arteries you found arising from the transverse part of the aortic 

 torch. 



The innominate artery on the right side ; the left common carotid and left 

 subclavian on the left side. 



3 1 . Name the stages of the subclavian artery. 



The first stage is internal to the scalenus anticus muscle ; the second stage 

 is behind the muscle ; the third stage is from the outer margin of the muscle to 

 the lower border of the first rib. 



32. Name the branches of the subclavian artery. 



(i) The internal mammary ; (2) the vertebral ; (3) the suprascapular ; (4) the 

 superior intercostal ; (5) the transversalis colli. 



33. Wlicre would you find for ligation tlie internal mammary artcrv .' 



A finger's breadth to the right or left of the sternum, in the third or fourth 

 intercostal space. 



34. How does the vertebral artery get to the base of the brain .' 



It passes through foramina in the transverse processes of the cervical 

 vertebrae, and through the foramen magnum. 



35. If the common carotid artery were ligated, by what two collateral clianncls 

 would the blood circulate ? 



First, through the thyroid arch. Second, through the occipito-intercostal 

 arch. 



36. How is the thyroid arch formed f 



By anastomosis between the superior thyroid branch of the external carotid 

 artery and the inferior thyroid branch of the subclavian artery. (Fig. 38.) 



37. Ho^v is the occipito-intercostal arcli formed ? 



By an anastomosis between the princeps cervicis of the occipital, and the deep 

 cervical branch of the superior intercostal artery. 



38. What, if any, changes occur in these collateral arches ? 



They become much larger, since growth is the correlative of function. 



