TRANSVERSE SECTIONS 



III 



of the plica vena; cavas (caval mesentery) located to the right of the mesentery 

 (Fig. 107). This vein now carries blood direct to the heart from the right pos- 

 terior cardinal and right subcardinal, by way of the liver sinusoids and the right 

 vitelline trunk (common hepatic vein). Eventually these four vessels form the 

 unpaired inferior vena cava. (For the development of the inferior vena cava see 

 Chapter IX). 



First aortic arch SecsscVs pocket 

 Second aortic 

 Pharynx 

 Thyreoid 

 Third aortic arch 



ni. carotid artery 



Xolochord 



Fourth aortic arch 

 102 

 Fifth aortic arch and 

 pulmonary artery 

 103 

 Esophagus 

 104 

 Trachea 

 105 

 R. lung 

 106 



107 J 



Stomach 



10S 



Cceliac artery 



log 

 Ventral pancreas 

 Dorsal pancreas 

 Gall bladder 



L. umbilical vein 



Vitelline artery 



Pituitary body (pharyngeal 

 lobe) 



Optic recess 

 102 



Telencephalon 

 Ventral aorta 



~ Bulbus cordis 



Interventricular foramen 

 L. Jtorn of sinus venosus 



/L. umbilical vein 

 Tail-gut 



Cloaca 



107 

 Spinal cord 

 in 

 112 

 mS 



Metanepliric airfare 

 log 

 L. umbilical artery 



'A nastotnosis between 

 dorsal aorta: 



lllantoic stalk 

 L. dorsal aorta 

 110 Mesonephric duct 



Cephalic limb of intestinal loop 



Dorsal aorta I | Artery to mesoncphros 



Mesentery Caudal limb of intestinal loop 

 Fig. 100. — Reconstruction of a 6 mm. pig embryo in the median sagittal plane, viewed from the 

 right side. The numbered heavy lines indicate the levels of the transverse sections shown in Figs. 

 101-112. The broken lines indicate the outline of the left mesonephros and the course of the left um- 

 bilical artery and vein. The latter may be traced from the umbilical cord to the liver where it is sec- 

 tioned longitudinally. (Original drawing and reconstruction by Mr. K. L. Vehe). X i6j-£. 



Transverse Sections 



Having acquainted himself with the anatomy of the embryo from the study 



of dissections and reconstructions, the student should examine serial sections cut 



in the plane indicated by guide lines on Fig. ioo. Refer back to the external 



structure of the embryo (Fig. 88), to the lateral dissection of the organs (Fig. 



