TEE CIRCULATTON. 



403 



lungs. The worn-out tissue of the body is also taken up by the 

 blood, and carried off through the bowels, lungs, kidneys, and 'skin, 

 which are the natural sewers or depurative channels of, the body. 

 The quantity of blood that a horse contains is about ^o of his weight. 



Fig. 693, — Distribution of the Anterior Aorta. 



1. Anterior aorta; 3. Left axillary artery; 3. Bight axillary artery; 4. Dorsal artery; 5. 

 Subcostal artery; 12. External thoracic artery; 14. Carotid artery; 17. Posterior aorta. A, 

 pulmonary aorta; B, trachea; E, superior branch of the lliospinal 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; O, F, great pectoral and 

 sterno-prescapularis muscles turned downward. 



r 



A horse weighing 1,000 pounds would therefore have about 100 

 pounds of blood, or nearly 50 quarts. Fat horses have proportion- 

 ately less blood than those that are lean ; and it is claimed that 

 wild animals generally have more blood in proportion than the 

 domestic ones. Forty pounds of blood have been taken from 

 medium-sized horses without serious injury ; and it requires the 

 extraction of about Vs of the total weight before life is destroyed. 

 It is a remarkable fact that this large amount of blood in the body 

 makes its entire round of circulation in the short period of from iwo 



