286 



STUDY OF PIG EMBRYOS. 



X 



circulation. The aorta is surrounded by mesenchyma, and to this are, so to 

 speak, appended the large Wolffian bodies, W.B, one on each side. From the 

 dorsal region of the embryo to the umbilical cord extends the somatopleure or 

 body-wall, Som, which, like that around the pericardial chamber, consists of an 



Sp.c. 



V.U.D. 



Um 



Om.min. 



G.bl. 



V.U.S 



FIG. 198. PIG, 12.0 MM. TRANSVERSE SERIES 5, SECTION 633. 



Ao, Dorsal aorta. EC, Ectoderm. G, Spinal ganglion. G.bl, Gall-bladder. Gen, Anlage of genital gland. 

 Li, Liver, mes, Somatic mesenchyma. msth, Somatic mesothelium. ^Y, Spinal nerve. Nch, Notochord. 

 Om.maj, Omentum ma jus. Om.min, Omentum minus. Som, Somatopleure. Sp.c, Spinal cord. St, 

 Stomach. Um, Umbilical cord. V '.card, Posterior cardinal vein. V.C.I, Vena cava inferior. Vert, Anlage 

 of w. '?-;... V.U.D, Right umbilical vein. V.U.S, Left umbilical vein. W.B, Wolffian body. X 22' 

 diams. 



external ectoderm, Ec^ middle mesenchyma, mes, and an internal mesothelium, 



'sth. It is important fur\ the student to understand the arrangement of the germ- 



rs in the sonutopleureX The mesothelium is commonly known in the descrip- 



:natomy of the :-<Hnlt ,,s the peritoneal epithelium. The peritoneal membrane 



