THM CIItCULATOBY APPABAT08 OF BIRDS. G49 



The arteries of the pelvic limhs— the /emoraZ or crural, in passing above the kidneys, 

 furnish the renal arteries; they then leave the pelvis by tlie great ischiatio notch, im- 

 mediately behind the coxo-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 continued by the popliteal vessels. These 

 arteries throw off articular ramusoules, the medullary 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 inter- 

 space 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 whose ramifications are dis- 

 tributed among the muscles and quills of the tail. 



Article III. — The Vein3. 



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 vense cavss and one posterior vena cava. 

 They enter a particular compartment, a kind of sinus, in the auricle. 



The anterior vense cavm 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 

 placed on the sides of the trachea; while the carotids are placed in the median line, 

 beneath the long flexor muscle of the neck. 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, there may be cited the femoral or crural veins. 

 These vessels do not accompany the corresponding arteries; not entering the pelvic 

 cavity by the great isehiatic notch, they pursue a course analogous to that described for 

 tiiese 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. 



Akticle IV. — The Lymphatics. 



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

 with elsewhere than in the cervical region ; the former are abundant in the viscera, and 

 unite in such a manner as to form two thoracic ducts. These ducts commence at the 

 cceliac trunk, and pass along the lower face of the lung, receiving the lymphatics of that 

 organ and those of the wings, and finally open into tlie jugular veins, a little in front of 

 their union with the axillary veins. A transverse branch forms a communication 

 between the two thoracic ducts, towards theii- termination. 



