734 



THE CIRCULATION. 



supply of nutritious matter, the blood goes to the heart and lungs 

 to be oxygenized by contact with the air, and thus be continued 

 through the heart and arteries as before explained. The system 

 takes up its material for its wear and tear through the capillaries 

 or hair-like tubes, which are interposed between the two great 



Fia. 624. Distribution of the anterior aorta. 



1. Anterior aorta; 2. Left axillary artery; 3. Right axillary artery; 4. Dorsal 

 artery; 5. Subcostal artory; 12. External thoracic artery ; 14. Carotid artery; 17. 

 Posterior aorta; A. Pulmonary aorta; B. Trachea; E. Superior branch of the ilio- 

 spinal muscle; F. Inferior branch of the same; G. Great complexus muscle; I, I. 

 Originating aponeurosis of the splenius and the small anterior serratus muscles; 

 N. Sterno-maxillaris muscle; 0, P. Great pectoi al and sterno-prescapularis muscles 

 turned downward. 



divisions of the vascular system, arteries and veins. These little 

 tubes are so small that they are from y^ to ^Vfr of an inch in 

 diameter. The smaller are found in the retina of the eye and 

 brain. The larger in the liver and lungs. The worn-out tissue 



