FIG. 275. PROFILE VIEW OF A HUMAN EMBRYO OF ABOUT THREE OR FOUR WEEKS, SHOWING THE 

 PRINCIPAL ARTERIES AND VEINS. (His.) 



1, 2, 8, 4, 5, the secondary cerebral vesicles ; hyp, hypophysis ; ot, otic vesicle ; mn, mandibular 

 arch ; Ig, lung-rudiment ; st, stomach ; W.d., Wolman duct opening into cloaca ; I, II, III, IV, V, the 

 arterial arches springing from b.a., bulbus arteriosus; p, pulmonary artery; d.C., duct of Cuvier ; 

 ch, notochord. 



FIG. 276. DIAGRAM TO SHOW THE DESTINATION OF THE ARTERIAL ARCHES IN MAN AND MAMMALS. 



(Modified from Rathke.) 



The truncus arteriosus and five arterial arches springing from it are represented in outline only, 

 the permanent vessels in colours those belonging to the aortic system red, to the pulmonary system 

 blue. This diagram is retained here in order to present the traditional account of the development 

 of five aortic arches handed down from Kathke. The recent views are presented in fig. 277. 



