736 THE CIRCULATORY APPARATUS OP BIRDS. 



teric leaves the subsacral artery, and, by some ramuscules, reaches the rectum and 

 cloaca. 



Shortly before its termination in three branches, the aorta gives off an artery 

 that crosses the middle portion of the kidneys, leaves the abdominal cavity, and 

 becomes distributed to the anterior muscles of the thigh, after detaching the 

 epigastric artery. The latter proceeds forward, beneath the skin of the abdomen, 

 and anastomoses with the ramifications of the thoracic artery. 



The arteries of the pelvic limbs — the femoral or iUac, in passing above the 

 kidneys, furnish the renal arteries ; they then leave the pelvis by the sacro-sciatic 

 foramen, immediately behind the coso-femoral articulation. Placed beneath the 

 muscles on the posterior face of the thigh, in following the branches of the 

 lumbo-sacral plexus as far as the femoro-tibial articulation, they are then con- 

 tinued by the popliteal vessels. These arteries throw off articular ramuscules, 

 the nutrient artery of the tibia, and a long branch to the muscles on the posterior 

 aspect of the leg ; they are placed in the groove resulting from the junction of 

 the tibia and fibula, and pass through the osseous interspace to form the anterior 

 tibial arteries. 



The middle sacral continues the aorta to the bottom of the pelvis ; when it 

 arrives below the last coccygeal vertebra, it forms a kind of arch, the ramifications 

 of which are distributed among the muscles and quills of the tail. 



Article III. — The Veins. 



As in Mammals, the veins are distinguished as belonging to the great and 

 lesser circulation. 



The veins of the great circulation are collected into three trunks that open 

 into the right auricle of the heart ; there are two anterior vena, cavm and one 

 posterior vena cava. They enter a particular compartment — a kind of sinus— in 

 the auricle. 



The anterior vencB cava!' collect the blood from the subclavian arteries and 

 those of the head. The jugular veins, which are their principal branches, are 

 not the satellites of the carotid arteries, as in the larger domesticated animals ; 

 they are superficial and situated on the sides of the trachea ; while the carotids 

 are placed in the middle line, beneath the longus colli. They are not of the 

 same calibre in all species, the right jugular being more voluminous than the 

 left ; there is always, however, a transverse anastomosis between the two jugulars, 

 below the base of the cranium. 



The posterior or inferior vena cava commences at the anterior extremity of 

 the kidneys, and passes forwards, traversing the right portion of the liver, 

 receiving the hepatic veins, and enters the right auricle. 



Among the branches forming it may be cited the femoral or iliac imns. 

 These vessels do not accompany the corresponding arteries, and therefore do 

 not enter the pelvic cavity by the sacro-sciatic foramen, but pursue a course 

 analogous to that described for these vessels in Solipeds, in passing beneath the 

 crural arch. 



In Birds furnished with a crest and mandibles, the skin of the head is provided 

 with an excessively rich vascular plexus. 



Article IV. — The Lymphatics. 

 Birds possess lymphatic vessels and glands. The latter are few, and are scarcely 



