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 

 A. cervicalis 



Sympathetic nerve-cord. 

 I Eighth rib. 



Truncus oesophageus dorsalis. 



)rofunda. 



Thoracic duct. ,' / , j 1 Diaphragm. 



Truncus brachiocephalicus. ' [ j Truncus oesophageus ventralis. 



Pericardium. ' ' 



I I 



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.], ppaxlwv (brachion) [Gr.], the arm (above the elbow). Cephalicus 

 [L.], /ce^aXtKos (cephalicns) [Gr.], pertaining to the head (K€<pa\ri). 



