VEINS OF THE THORACIC LIMB 



593 



The diploic veins (Vense diploicse) are anastomosing channels in the spongy 

 su])stance of tlie cranial bones. Their walls are thin, consisting in many places 

 only of the endothelium, and they have no valves. Some open inward into 

 venous sinuses, others into extracranial veins. 



Spinal Veins 

 Two longitudinal spinal veins or sinuses (Sinus colunmae vertebralis) extend 

 along the floor of the vertebral canal, one on either side of the superior conunon 

 ligament. They are continuous in front with the basilar plexus. They lie in the 

 grooves on the bodies of the vertebrae and are connected by a series of transverse 

 anastomoses which pass between the central part of the bodies of the vertebrae 

 and the superior common ligament or in channels in the bone. Thej^ receive veins 

 from the spinal cord, the dura mater, and the bodies of the vertebrae (\"en8e basis 

 vertebrae). Through the intervertebral foramina 

 efferent vessels connect with the vertebral, inter- 

 costal, lumbar, and lateral sacral veins. 



VEINS OF THE THORACIC LIMB 



The brachial vein (Y. brachialis) is a satellite 

 of the extrathoracic part of the brachial artery. 

 It arises at the inner side of the distal end of the 

 shaft of the humerus and passes upward in the 

 arm behind the artery under cover of a layer of 

 fascia and the posterior superficial pectoral mus- 

 cle. At the shoulder it is ventral to the artery, 

 crosses the anterior border of the first rib, and 

 concurs with its fellow and the two jugulars in 

 the formation of the anterior vena cava. The 

 roots of the vein are somewhat variable, but most 

 often four radial veins in addition to a large ob- 

 lique branch from the cephalic unite in its forma- 

 tion. Its tributaries correspond in general to the 

 branches of the artery, but a few differences are 

 worthy of notice. The thoracico-dorsal vein 

 joins the brachial directly or opens into the deep 

 brachial. The external thoracic or "spur" vein 

 (V. thoracica externa) is a large vessel which 

 arises in the ventral wall of the abdomen, passes 



Fig. 465. — Spixal Vessels of Horse. 

 The vertebral canal has been opened 

 by sawing off the arches. The nerve- 

 roots are cut on one side and the spinal 

 cord turned over to right. /, Ventral 

 or middle spinal artery; 2, reinforcing 

 branches from vertebral, intercostal, or 

 lumbar arteries (according to region); 3, 

 longitudinal vertebral sinuses; a, ventral 

 surface of spinal cord; b, dura mater (cut) ; 

 c, nerve-roots; d, superior common liga- 

 ment. (After EUenberger, in Leisering's 

 Atlas.) 



forward (embedded more or less in the panniculus) 



along the outer border of the posterior deep pectoral muscle, and joins the brachial 



vein near the first rib. It often communicates with the subscapular vein. 



The cephalic vein (V. cephalica) arises at the inner side of the carpus as the 

 continuation of the internal superficial metacarpal vein. It runs upward on the 

 deep fascia of the forearm at first in the furrow between the flexor carpi internus 

 and the radius. Toward the middle of the forearm it inclines gradually forward 

 on the inner surface of the radius, accompanied by a cutaneous branch of the median 

 nerve, and arrives at the insertion of the biceps. Here it detaches a large branch 

 (Ramus communicans) which passes upward and backward over the inner insertion 

 of the biceps, the posterior radial artery, and the median nerve, and joins the ])ra- 

 chial vein. The vein to this point is often termed the internal subcutaneous vein of 

 the forearm (V. cephalica antebrachii). It is continued (as the V. cephalica 

 humeri) in the furrow between the mastoido-humeralis and the anterior superficial 

 pectoral with a branch of the inferior cervical arterv, crosses the deep face of the 

 38 



