306 ANATOMY OF THE RABBIT 



6. The branches of the common carotid artery may be traced in 

 the anterior portion of the ventral surface of the neck as follows: 



(a) The internal carotid artery (a. carotis interna) is a small 

 vessel given off from the dorsal wall (pp. 172, 361). 

 The trunk then passes forward as the external carotid 

 (a. carotis externa). 



The internal carotid artery passes dorsad, medial to the styloglossal 

 and stylopharyngeal muscles, to the base of the skull and enters the 

 external carotid foramen, traverses the carotid canal, and enters the 

 cranial cavity through the foramen lacerum to supply the brain. 



At its very beginning, the internal carotid artery is very slightly 

 distended as the carotid sinus, an organ which, though hardly noticeable 

 in ordinary dissection, is important physiologically. It is a sensory 

 receptor, stimulation of which by increased blood-pressure causes 

 impulses to pass through fibres in the ninth, tenth, and eleventh cranial 

 nerves and to produce reflex vasodilatation. 



In the angle between the origins of the external and the internal 

 carotid arteries is situated another organ too minute for observation 

 in the gross, the carotid body or glomus caroticum. This is stimulated 

 by chemical changes in the blood and sends impulses through a special 

 branch of the glossopharyngeal nerve to alter blood-pressure, heart-beat, 

 and respiration. The branch in question, the first to separate from the 

 ninth nerve as it emerges from the cranium, is the intercarotid nerve or 

 nerve of Hering. 



(b) The occipital artery (a. occipitalis) passes from the dorsal 

 wall to the posterior portion of the head. 



The stylohyoideus major, a slender muscle arising with 

 the digastricus from the stylohyoid ligament and inserted 

 on the greater cornu of the hyoid, should be divided. The 

 tendon of the digastricus may be reflected. 



(c) The lingual artery (a. lingualis) arises from the ventral 

 wall and passes forward into the tongue. 



The hypoglossal nerve crosses the ventral surface of the artery and 

 should be kept intact. 



(d) The external maxillary artery (a. maxillaris externa) is 

 given off immediately in front of the lingual artery, some- 

 times in common with it. It passes forward on the medial 

 surface of the ventral border of the mandible (medial to 

 the digastricus), giving branches to the submaxillary gland 

 and to the muscles of mastication. The vessel has been 



