170 



THE FOURTH DAY. 



[CHAP. 



into a part nearer the heart which is called the sinus venosus 

 (Fig. 53, S.V.\ and into a part surrounded by the liver 

 which is called the ductus venosus. Beyond, i.e. behind the 

 liver, the ductus venosus is directly continuous with the 

 omphalo-mesaraic veins, or as we may now say, vein, for the 

 right trunk has become so small as to appear a mere branch 

 of the left. (Fig. 53, Of.) 



We saw that on the third day the ductus venosus, while 

 running through the liver, exhibited numerous 



bulgmgs 



FIG. 53. 



DlAGBAM OF THE VENOUS ClKCULATION AT THE COMMENCEMENT OF THE FlFTH 



DAY. 



H. heart. 2). O. ductus Cuvieri. Into the ductus Cuvieri of each side fall /. the 

 jugular vein, or superior cardinal vein, Su. V. the superior vertebral vein, W. 

 the vein from the wing and C. the inferior cardinal vein. S. V. sinus 

 venosus. Of. omphalo-mesaraic vein. U. umbilical vein, which at this 

 stage gives off branches to the body- walls. 



