THORAX AND ABDOMEN OF THE HORSE 



39 



carotid arteries have blended at their origin to form a bicarotid 

 trunk. 



Truncus brachiocephalicus communis. — If, as has been stated 

 above, the common brachio-cephalic ^ trunk is the result of fusion of 

 four vessels, all of which, in the primitive arrangement, have independent 



A. intercostalis. 



Aorta. 



M. longus colli. 

 A. intercostalis suprema 



A. transversa colli. 



A. cervicalis 

 profunda. 



Sympathetic nerve-cord. 

 1 Eighth rib. 



Truncus oesophageus dorsalis. 



N. Vagus. 



■ Thoracic duct. ' / i | 1 Diaphragm. 



Truncus brachiocephalicus. ' | ' Truncus oesophageus ventralis. 



Pericardium. ' ' 



N. phrenicus. A. pulmonalis. 



Fig. 19. — Dissection of the thoracic contents from the left side, after 

 removal of the lung. 



origin from the aortic arch, it will not be unreasonable to expect con- 

 siderable individual variation in the length of the common trunk so 

 formed. Sometimes, indeed, the trunk as such does not exist, the left 

 subclavian and brachio-cephalic arteries arising from a common point 

 on the convex side of the aortic arch. 



1 Brachium [L.], ^paxiuv (brachion) [Gr.], the arm (above the elbow). Cephalicus 

 [L.], Ke<pa.\iKl)% (cephalicos) [Gr.], pertaining to the head ((ce^aXiJ). 



