MAN. 



331 



and the duct of the compact pancreas joins the bile duct in the 

 Avail of the duodenum. 



4. Circulatory System. Three arteries come off from the aortic 

 arch, (a) innominate, from which right subclavian and right 

 common carotid arise, (b) left common carotid, (c) left subclavian. 

 The fate of the embryonic aortic arches is shown in Fig. 103. 



1st ( =mandibular) arches become ophthalmic branches of external carotids. 



( middle 

 " | meningeal 



internal carotids. 



2nd ( = hyoid) 



3rd ( = 1st branchial) 



4th ( = 2nd branchial) 



left 

 right 



5th ( = 3rd branchial) 

 left \ 

 right / 



( aortic arch 



< represented by a very variable arteria 



f aberrans. 



/ pulmonary artery. 

 1 obliterated. 



Veins. The development of the caval system is illustrated by 

 There are to begin with anterior and posterior car- 



Fig. 104. 



Fig. 104. MAN. Diagram to explain Development of Systemic Veins 

 (from Macalister). Three successive stages are represented, R.C. and 

 L.C, Cuvierian veins; R.V.I., L.V.I., vena innominata ; S.V.C., 

 superior vena cava ; sup. *, superior intercostal; h.a~, hemi-azygos. 



dinals, which, as in the adult Dogfish (cf. p. 165),unite together 

 on each side to constitute a Cuvierian vein which opens into the 



