384 CIRCULATING SYSTEM OF BIRDS. 



the right auricle, and from thence is carried to the right ventricle, 

 which sends it to the lungs through the pulmonary arteries ; it 

 returns again to the heart, enters the left auricle, -and completes 

 the circulation by passing into the left ventricle, from which it set 

 out. The heart has the same form, the same structure, the same 



.* Lingual artery. 



Trachea 



Sacral artery. Cloaca. 



FIG. 202 ARTERIAL SYSTBM OF BIRD. 



position, and the same coverings as in the Mammalia ; the walls 

 of the left ventricle are extremely thick, and the right ventricle 

 surrounds it on the right, and below, without prolonging itself to 

 the point of that organ. The Aorta at its origin divides into 



