80 F. W. THYNG 



of the large intestine. In the umbilical cord, after again crossing 

 the gut (on the left side of the small intestine), it follows the 

 yolk-stalk. In a 17 mm. human embryo studied by Tandler 

 ('03) the origin of this artery is opposite the 21st intersegmental 

 (1st lumbar) artery. 



On a level with the 2nd lumbar pair of dorsal intersegmental 

 arteries the inferior mesenteric (A.mes.i.) arises from the aorta. 

 It is a small ventral visceral branch, extending ventrally and 

 somewhat caudally between the aortic bodies (of Zuckerkandl) 

 into the dorsal mesentery. In the dorsal mesentery it gives off 

 several branches which ramify in the region of the colon. Tand- 

 ler (-03) found this artery in a 17 mm. human embryo arising 

 from the aorta at the level of the 23d intersegmental (3d lumbar) 

 artery. 



That the arteries of the gut migrate cephalo-caudad was 

 demonstrated by Mall ('91 and '97), but comparison of the origins 

 of these arteries in this embryo with those described by Tandler 

 ('03) in an embryo of approximately the same length, indicates 

 that the rate of migration is somewhat variable, or we may have 

 to do merely with variations in the point of origin, such as have 

 been demonstrated for the superior mesenteric artery. 



Just caudad of the pleural cavities and on a level with the 10th 

 thoracic pair of dorsal intersegmental arteries, there appears a 

 left lateral visceral artery. It extends from the aorta laterally 

 and caudad first along the medial border of, and then through, 

 the suprarenal gland to the Wolffian body. Apparently this 

 vessel becomes the left inferior phrenic artery which furnishes a 

 superior suprarenal branch in the adult. Another pair of lateral 

 visceral (mesonephric) arteries (A.s.-r.) presumably the middle 

 suprarenal of the adult leaves the aorta near the origin of the 

 superior mesenteric artery. This pair of vessels extends laterally 

 in a cephalo-dorsal direction to the anlagen of the suprarenal 

 glands. 



Beginning just caudad of the place of origin of the superior 

 mesenteric artery the left components of four successive pairs of 

 lateral visceral (mesonephric) arteries are seen in the reconstruc- 



