10 PHYSIOLOGY. 



CIRCULATION. 



A function whose end is the general movement of the blood 

 in the body of animals. This movement consists in carrying 

 the nutritive or arterial blood through all the organs, and in 

 conveying to a respiratory apparatus this same liquid, de- 

 prived of the elements of nutrition, and loaded with matter 

 which should be expelled. The circulatory apparatus offers 

 for consideration the heart and the blood vessels. 



The Heart. 



The principal agent in the impulsion of the blood, placed 

 in man within the cavity of the thorax, between the lungs, 

 the point below, a little forward and to the left. It consists 

 of two sides, which have no communication with each other : 

 the right side, which is always filled with venous blood, and 

 in which is the right, auricle, communicating only with the 

 right ventricle ; and the left side, filled with arterial blood, in 

 which is the left auricle, communicating only with the left 

 ventricle. 



Blood Vessels. 



These are of three kinds. The arteries, carrying the blood 

 of the heart to the parts. The veins, returning it from the 

 parts to the heart. The capillary vessels, forming a commu- 

 nication between the veins and the arteries. 



Principal Arteries. 



These are the aorta and pulmonary artery. The aorta, 

 arising from the base of the left ventricle, terminates at the 

 bottom of the abdomen. It is the common trunk to the in- 

 nominata, the left carotid and the left subclavian, the c&liac, 

 superior and inferior mesenteric, the renal and the primitive 

 iliacs. The right carotid and right subclavian are formed by 

 the division of the innominata. The pulmonary artery, ari- 

 sing from the base of the right ventricle, is divided into two 

 branches, which lose themselves in the pulmonary tissue. 



Principal Veins. 



These are the vena cava superior and vena cava inferior, 

 formed by the union of the principal veins of the body, and 

 terminating, the former at the top and the latter at the base 

 of the right auricle ; and the pulmonary veins, two on each 

 side, extending from the lungs to the left auricle. 



