xxv] 



CIRCULATORY SYSTEM 



653 



" ventral subclavian." The " dorsal subclavian " possessed by most 

 Mammals is also found in Cetaceans, but it is distributed to the 

 ribs and their muscles as the "intercostal artery." 



13 



24 



Fio. 323. Diagram of arterial arches of Mammals, viewed from the ventral 



aspect. 



A. Of all Mammals except Cetaceans. 



i, n, in, iv, v, vi. First to sixth arterial arches. 12. Ventral carotid 



(small or absent). 13. Common carotid (dorsal carotid). 14.. Syst- 

 emic arch. 17. Dorsal aorta. 18. Ductus arteriosus which in the 

 embryo connects the pulmonary and systemic arteries. . 19. Pulmonary. 

 20. Innominate. 22. Subclavian (dorsal type). 24. Coeliac. 



B. Of Narwhal, representing Cetaceans. 



i, n, in, iv, v, vi. First to sixth arterial arches. 12. Ventral carotid 



(small). 13. Common carotid (dorsal carotid). 14. Systemic arch. 

 17. Dorsal aorta. 18. Ductus arteriosus. 19. Pulmonary. 20. Innomin- 

 ate. 21. Subclavian (ventral type). 22. Intercostal (equivalent to 

 eubclavian of dorsal type). 24. Coeliac. 



