104 ANIMAL PHYSIOLOGY. 
common trunk of the allantoic and vitelline veins (ductus veno- 
sus) passes through the liver, where it is said the ductus veno- 
Fie. 119.—Diagrams of the aortic arches of mammal (Landois and Stirling, after Rathke). 
1. Arterial trunk with one er of arches, and an indication where the second and third 
pairs will develop. 2. Ideal stage of five complete arches ; the fourth clefts are shown on 
the left side. 3. The two anterior pairs of arches have disappeared. 4. Transition to the 
final stage. .A, aortic arch; ad, dorsal aorta ; az, subclavian or axillary artery ; Ce, ex- 
ternal carotid ; Ci, internal carotid ; dB, ductus arteriosus Botalli; P, pulmonary artery ; 
S, subclavian artery ; ta, truncus arteriosum ; v, vertebral artery. 
sus gives off and receives branches. The ductus venosus Aran- 
tii persists throughout life. (Compare the various figures illus- 
trating the circulation.) 
Fia. 120.—Diagram illustrating transformations of aortic arches ina lizard. A; a snake, B; 
ird,C; a mammal, D. Seen from below. (Haddon, after Rathke.) a, internal caro- 
tid ; 6, external carotid ; c, common carotid. A. d, ductus Botalli between the third and 
fourth arches; e, right aortic arch ; ts subclavian ; g, dorsal aorta; h, left aortic arch ; 
i, pulmonary artery ; k, rudiment of the ductus Botalli between the pulmonary piety and 
the aortic arches. B. d, right aortic arch; e, vertebral artery ; P left aortic arch; h, 
pulmonary artery ; 7, ductus Botalli of the latter. C. d, origin of aorta; e, fourth arch of 
the right side (root of dorsal aorta); f, right subclavian; g, dorsal aorta; h, left subclavian 
(fourth arch of the left side) ; i, pulmonary artery ; k and 1, right and left ductus Botalli 
of the pulmonary arteries. D. d, origin of aorta ; e, fourth arch of the left side (root of 
dorsal aorta); f, dorsal aorta; g, left vertebral artery ; h, left subclavian ; 7, right sub- 
clavian (fourth arch of the right side); k, right vertebral artery ; 1, continuation of the 
right subclavian ; m, pulmonary artery ; n, ductus Botalli of the latter (usually termed 
ductus arteriosus). 
