THE VEINS. 115 



Arteria Princeps Cervicis, br. of occipital, from the external carotid, with 

 the Vertebral, br. of subclavian, and the Profunda Cervicis, br. of the 

 superior intercostal, from the subclavian. 



What is the Longest Anastomosis in the Body? That between the 

 subclavian and the external iliac by the anastomosis of the Superior Epigastric., 

 br. of the internal mammary, with the Deep Epigastric, br. of the external 

 iliac. 



[The circle of Willis has been described on page 106 ; the palmar and plantar 

 arches on pages 108 and 113 respectively; and the anastomosis on the mem- 

 brana tympani on page 105.] 



THE VEINS. 



What are the Veins ? Vessels carrying blood towards the heart. Their 

 walls are composed of 3 coats, an internal, serous; a middle, muscular; and 

 an external, fibrous. They all carry carbonized or venous blood, except the 

 pulmonary veins, which bring oxygenated blood to the left side of the heart. 

 The deep veins accompany the arteries, generally in the same sheath, and are 

 given the same names. The secondary arteries, as the radial, ulnar, brachial, 

 etc., have each two veins, called Vena Comites. The superficial veins are 

 usually unaccompanied by arteries, and lie, as a rule, between the layers of 

 the superficial fascia, terminating in the deep veins. Many veins are so irreg- 

 ular in their origin that they cannot be accurately described; they all anasto- 

 mose with each other much more freely than do the arteries. 



What are Sinuses ? They are venous channels, differing from veins in 

 structure, but answering the same purpose. Those of the cranium are formed 

 by the separation of the layers of the dura mater. 



How are the Veins divided ? Into the Pulmonary, Systemic, and Portal 

 Systems ; the latter being an appendage of the systemic, its capillaries rami- 

 fying in the liver. 



What Veins have no Valves? The vense cavae, hepatic, portal, renal, 

 uterine, ovarian, cerebral, spinal, pulmonary, umbilical, and the very small 

 veins. 



Name the principal Veins of the Head and Neck. They are the 

 (i.) Exterior veins. (2.) Veins of the diploe and cranium. 



Facial. Veins of the Diploe. Transverse Sinus. 



Temporal. Cerebral and Cerebellar. Cavernous Sinus. 



Internal Maxillary. Superior Longitudinal Sinus. Occipital Sinus. 



Temporo-maxillary. Inferior Longitudinal Sinus. Superior Petrosal Sinus 



Posterior Auricular. Straight Sinus. Inferior Petrosal Sinus. 



Occipital. Circular Sinus. Lateral Sinus. 



