TIII: . i. N rr.uittn \I:\A CAY A. 001 



aorta .' The terminal extremity of its inflection crosses the oesophagus and 

 tr.ichca t tire right, ami is included b, 'tween these two tabes 011 the one 



.lid the right layer of the mediastinum on the other. 

 lt> r....t> an- suiiie branches emerging from the spinal and psoas nn 

 and which are not usually in direct communication with the posterior vena 

 cava. as in IM.ui and the other animals. 



During its progress, it receives the first lumbar and the satellite veins 



of all the aortic intercostal arteries, right and left. But when the small 



i/ynos is prolonged backwards beyond the posterior extremity of the 



Mih -..stal artery, that vessel, as we have already seen, forms the confluent of 



tain Jiuinli r of left posterior intercostals. 



JUGULAR VEINS. 



The jugular is a satellite vein of the carotid artery. 



'it. It commences behind the inferior maxilla, below the articula- 

 tion of the jaw, by two large roots: the superficial temporal trunk and the 

 infi ruerl maxillary cein, which correspond to the two terminal branches of 

 the external carotid artery (Fig. 290). 



x itiiw J)!i-i'i-tiu. This vessel passes downward and backward, 

 lodged at tir&t in the substance of the parotid gland, afterwards in the 

 muscular interstice designated the jugular channel, and which is comprised 

 1- t.u ( 11 the adjacent borders of the levator humeri (mastoido-humeralis) and 

 >ti rno-iuaxillaris muscles. Reaching the inferior extremity of the neck, it 

 terminates in the fcdlowing manner (Fig. 290) : 



Tt-nninution. On arriving near the entrance to the chest, the two 

 jugulars unite in foiming a vessel named the confluent of the jugulars. This 

 confluent, into the sides of which open the two axillary veins, is comprised 

 between the t .vo first ribs, and situated below the trachea, in the middle of the 

 lymphatic glands at the opening of the chest. Fixed by fibrous bonds to the 

 1) mi-ing parts, and particularly to the two first ribs, the walls of the 

 jugular confluent do not collapse when the venous system is in a state of 

 vacuity : an anatomical peculiarity which it is necessary to understand, in 

 order t > explain the manner in which air obtains an entrance into the circu- 

 y system when the jugular or axillary veins are opened, as well as 

 affording an indication how to prevent this serious accident. 



/,'/.///.///*. At its upper extremity, the jugular vein is surrounded by tho 

 j.arotidcal tissue. For the remainder of its extent, it is covered externally 

 by the subcutaneous muscle of the neck, and by tho branches of the cervical 

 plexus which creep on the external surface of that muscle. Inwardly, 

 its relations vary as wo consider its situation, above or below : above, it 

 responds to the eubscapnlo-hyoideus muscle, which separates it from tho 

 common carotid and its satellite nerves; in its inferior moiety, it is in 

 direct relation with that vessel, which is above it, as well as with the trachea, 

 and even, though only on the left side, with the oesophagus. 



COLLATERAL AFFLUENT VESSELS. Tho collateral veins which go to tho 



jugular from its origin to its termination, are : 1, MaxiUo-musndar veins; 



2, Posterior auricular vein ; 3, Occipital vein ; 4, External maxillary, or ylosto- 



\n ; 5, Thyroid vein; 6, Cephalic vein ; 7, Parotideal and innominate 



"Inr l,riiit<-hes. 



A. MAXILLO-MUSCULAR VEINS. Two in number, corresponding to the 



3 tin times the azygoj is situated between the uorta ami the tlmmf ic duct When 

 tin.' l.ut.T lies to the left side, it iu in direct contact with tin- |>oetrrior aorta. 



