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PROCEEDINGS OF THE NATIONAL MUSEUM 



the adult animal a common trunk with the carotid artery exists as the 

 innominate artery. 



The axillary artery is derived from the distal portion of the primary 

 subclavian artery. 



Hochstetter (1890) has shown that the definitive subclavian arises 

 from the ventral ends of the carotid arches, as had previously been 

 announced by Mackay (1887), but that the primary arteries to the 

 wing-bud have their source directly from the dorsal aorta, as seg- 

 mental vessels, and that the primary subclavian then completely 

 disappears. This primary vessel was regarded by Hochstetter as the 

 mammalian homologue. Sabatier (1874), Rathke (1850), and others 

 tended to add confusion to the matter by misplacing or improperly 



Figure 109. — Aortic arch system in Gallus, showing primary and secondary subclavians 

 (ventral view, modified after Krassnig). Explanation of symbols: I, primary subclavian 

 artery; II, secondary subclavian artery; 3, carotid arch; 4, systemic arch; 6, pulmonary 

 arch; c.d., dorsal carotid artery; d.a., abdominal aorta; d.c, ductus caroticus; r.a., radix 

 aortae; s, subclavian artery; v, vertebral artery. 



locating the definitive subclavian, and it was not until Mackay and 

 Hochstetter published the results of their studies that any true light 

 was thrown upon the problem. In 1883, Brenner challenged the 

 views of Eathke and Sabatier by pointing out that owing to the 

 difference in the relative position of the vagus nerve, superior vena 

 cava, and subclavian, the latter in birds could not correspond in a 

 dorsal mode of origin with the subclavian of mammals. 



Hochstetter's work demonstrated that, although the definitive 

 vessel arises as a branch from the ventral part of the carotid arch, 



