650 



ARTERIAL ARCHES OF THE AMNIOTA. 



side. In most other types the origin of the subclavians is 

 carried upwards, so that they usually spring from a trunk 

 common to them and the carotids (arteria anonyma) (Birds and 

 some Mammals); or the left one, as in Man and some other 

 Mammals, arises from the systemic aorta just beyond the 

 carotids. Various further modifications in the origin of the 

 subclavians of the same general nature are found in Mammalia, 



A 



FIG. 366. DIAGRAMS ILLUSTRATING THE METAMORPHOSIS OF THE ARTERIAL 



ARCHES IN A LlZARD A, A SNAKE B, A BlRD C AND A MAMMAL D. (From 



Mivart ; after Rathke.) 



A. a. internal carotid ; b. external carotid ; c. common carotid ; d. ductus Botalli 

 between the third and fourth arches ; e. right aortic trunk ; /. subclavian ; g. dorsal 

 aorta; h. left aortic trunk; *'. pulmonary artery; k. rudiment of ductus Botalli 

 between the pulmonary artery and the system of the dorsal aorta. 



B. a. internal carotid ; b. external carotid ; c . common carotid ; d. right aortic 

 trunk; e. vertebral artery; / left aortic trunk of dorsal aorta; h. pulmonary artery; 

 i. ductus Botalli of pulmonary artery. 



C. a. internal carotid; b. external carotid; c. common carotid; d. systemic 

 aorta; e. fourth arch of right side (root of dorsal aorta);/, right subclavian; g. dorsal 

 aorta; h. left subclavian (fourth arch of left side); z. pulmonary artery; k. and /. 

 right and left ductus Botalli of pulmonary arteries. 



D. a. internal carotid ; b. external carotid ; c. common carotid ; d. systemic aorta ; 

 e. fourth arch of left side (root of dorsal aorta);/ dorsal aorta; g. left vertebral 

 artery; h. left subclavian artery; i. right subclavian (fourth arch of right side); k, 

 right vertebral; /. continuation of right subclavian; m. pulmonary artery; n. ductus 

 Botalli of pulmonary artery. 



