210 CIRCULATORY SYSTEM. 



The Anterior Vena Cava 



Forms the main trunk of (or common reservoir for) the veins 

 returning the blood from the head, neck, parietes of the chest, 

 and fore extremities. It is a short vessel, but one of considerable 

 volume, becoming remarkably bulky at its termination in the 

 summit of the right auricle. In relative position, the trachea 

 lies above it, the anterior aorta to its right, and it is with both 

 included in the interspace of the superior mediastinum. The an- 

 terior cava is principally formed by the concurrent union of the 

 jugular and axillary veins, and is situated at its formation within 

 the interval between the two first ribs, about midway between 

 the sternum and vertebrae : it also receives the pectoral, vertebra/, 

 dorso-cervical, and inferior cervical veins, and the vena azi/gos ; 

 which again augment its volume in its course to the heart. 



Jugular Vein, 



This forms the principal venous conduit from the head, along 

 the neck, corresponding in course and ramification to the carotid ; 

 consequently there exists a right and a left jugular vein, and 

 it is quite unimportant which is taken by way of description. 

 The jugular vein has its formation at the foramen lacerum basis 

 cranii, from the termination thereof the lateral sinus of the dura 

 mater, from which it receives the blood returned, principally from 

 the cerebrum, partly from the cerebellum. Concealed at its ori- 

 gin by the condyle of the jaw, it descends to the inner side and 

 behind the neck of the condyle, deeply buried under the parotid 

 gland : lower down, it makes its appearance behind the branch of 

 the jaw, and there joins the external carotid artery, along with 

 which it continues its passage into the neck. In this part of its 

 course it receives the following branches of importance — 1. The 

 AURICULAR VEINS, anterior and posterior, and also internal, 

 varying in their number and mode of termination, which are seen 

 descending over the root of the ear. 2. Th e temporal, a vein 

 of considerable size, running along the upper side of the temporal 

 artery. 3. The internal maxillary, a large vein keeping- 

 company with its artery ; and in its course receiving many small 

 veins — the palato-maxillary , infra and supra orbitar, ocular, in- 

 ferior maxillary, and deep temporal. 4. The parotideal, 

 numerous veins from the parotid, and some also from the sub- 

 maxillary gland. 5. Branches from the masseter and pterygoid 

 muscles. 



6. The occipital vein, a long flexuous branch descending 

 from the head along with the occipital artery, that brings blood 

 from the occipital sinuses, receives veins from the posterior lobes 



