LATER DEVELOPMENT OF VASCULAR SYSTEM 365 



a second venous ring is established around the aUmentary canal, 

 the lower portion of which is formed by the second anastomosis, 



Jnt. 



Oes. 



^- ft ,c.. ^^^:- 



S -/>^- 



/y/.^ 



Ko.rr/A i^' i 



A 



Ki/.s- 



■•?i' 



b: 



- ■ >. ■•.■-. / 



Kojn.^. 





\ 



^.^ ,VA 



rr.ir V /, ^ 



K \-kr.8. 



f I 



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y.i/. 



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f- 



Fig. 210. — Diagrams illustrating the development of the hepatic 

 portal circulation. (After Hochstetter.) 



A. About the fifty-eighth hour. • r j \ 



B. About the sixty-fifth hour; first venous rmg formed around 



the intestine. , , -, ,. , ^ ,, c + ,,^ 



C. About the seventy-fifth hour; the left limb of the hrst \e- 



nous ring has disappeared. "^ . . 



D. About the eightieth hour; the second venous rmg is estab- 



^^ E." About the one hundredth hour; the right limb of the second 

 venous ring has disappeared. , , , , .i w ^i 



F Hepatic circulation about the one hundred and thirtieth 

 hour, immediately before the disappearance of the intermediate 

 portion of the meatus venosus. ^ r^ ^ ^ c n • ;, + 



a i p , Anterior intestinal portal. D. C, Duct of Cuvier. mt., 

 Intestine M. V., Meatus venosus. CEs., CEsophagus. Pc, Fan- 

 creas St., Stomach. S. v.. Sinus venosus. V. c. i.. Vena cava 

 inferior V. h.. Hepatic veins. V. o. m., Omphalomesenteric vein. 

 V r 1 First venous ring. v. r. 2, Second venous ring. V. u. d., 

 Right umbihcal vein. V. u. s.. Left umbilical vein. 



