. The American journal of anatomy . human em-bryos of about 5 mm. Thus, in a mm. specimen, Ingalls hasfound several small veins ascending behind the intestine to jointhe dorsal anastomosis of the vitelline veins, which, it should benoted, is plexiform. These ascending veins probably give riseto the superior mesenteric vein. In a 7 mm. human embryo, ANOMALIES OF THE VITELLINE VEINS 105 Elze has shown that the superior mesenteric vein is a well-definedstem which empties into the spiral vessel formed from the peri-intestinal rings. The place of junction comes to lie on the leftside of the int
. The American journal of anatomy . human em-bryos of about 5 mm. Thus, in a mm. specimen, Ingalls hasfound several small veins ascending behind the intestine to jointhe dorsal anastomosis of the vitelline veins, which, it should benoted, is plexiform. These ascending veins probably give riseto the superior mesenteric vein. In a 7 mm. human embryo, ANOMALIES OF THE VITELLINE VEINS 105 Elze has shown that the superior mesenteric vein is a well-definedstem which empties into the spiral vessel formed from the peri-intestinal rings. The place of junction comes to lie on the leftside of the intestine, both in human embryos (Elze) and in pigembryos (Lewis, Thyng). In other words it has shifted ventrally,and the mesenteric vein appears to join the left half of the lowerperi-intestinal ring. Thus at the stage shown in Hiss figure,when the spiral vein has been formed from the peri-intestinalrings, the veins which unite near the intestine are the superiormesenteric vein and the fused vitelline trunk. On the other hand, , vu Fig. 1 Hiss diagram showing the formation of the portal vein, , parts of the right umbilical vein. , left umbilical vein. V. Ar.,ductus the place where the right and left vitelline veins unite is near the3rolk-sac, as shown in the reconstructions by Lewis and Thyng;and this is far removed from the area included in Hiss figure. The true relations of these vessels, as here described, havedoubtless been wTell understood by investigators of the venoussystem, but it is difficult to find an explicit account of recognized a vitelline vein coming from the yolk-sacand a mesenteric vein coming from the mesentery, but apparentlyhe did not consider the possibility that the mesenteric vein mightbe derived from a left vitelline vein. This possibility, suggested 1 For the use of the electrotype of this figure, and for many facilities for studyand investigation during my stay at the Harvard Laboratory, I am deeply i
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
