

P'IG. 176. PIG EMBRYO or 12.0 MM. RECONSTRUCTION FROM THE TRANSVERSE SECTIONS, SERIES 5. 



The figure illustrates chiefly the veins of the right side, and shows the right auricle and ventricle of the heart. 

 A, The right umbilical artery, only a small portion being drawn as it curves around the Wolffian duct, W.D. 

 a, Tip of aortic septum, which divides the aortic limb of the heart into the pulmonary aorta, P, and main 

 aorta, Ao; by a growth of the cardiac tissue, a, b, and c of the figure become joined, shutting off the space 

 around the base of the aorta; this space communicates by the interventricular foramen with the left ventricle, 

 and serves as the permanent or adult channel of communication between the true aorta, Ao, and the left 

 ventricle. All, Allantois. Ao, Aortic division of the aortic limb of the heart. Au, Right auricle, b, See 

 "<;." c, See"a."' card', Superior part of the cardinal' vein (the anlage of the azygos). card", Inferior part of 

 the posterior cardinal vein, d.i, Opening of the first gill-pouch into the pharynx, the pharynx being indicated 

 by dotted shading, cl.2, Opening of the second gill-pouch into the pharynx, cl.i,, cl.4, Entodermal portions 

 of the third and fourth gill-clefts, c.om, Dotted outline of the omental or lesser peritoneal cavity, d, Left 

 (hut of Cuvier. D.C, Right duct of Cuvier, the main venous trunk entering the heart from the right side. 

 D.V, Ductus venosus Arantii. F.W, Foramen epiploicum (of Winslow), drawn in black. F-Pp, Foramen, 

 drawn in black, between the pleural and peritoneal cavities. The foramen is bounded by the lung, liver, and 

 Wolffian body; the figure shows the pleural side of the opening. If we pass through the foramen as drawn we 

 reach the abdominal cavity. The outline of the pleural cavity is marked by a dotted line. Gen, Genital 

 tubercle, represented as somewhat displaced from the median line, which it really occupies. G.R, Genital 

 ridge. Jug', -/.?", Jugular or anterior cardinal vein. Li, Liver, l.s, Anlage of the lateral venous sinus. 

 i.\; Vein of the inferior maxilla or mandible. P, Pulmonary division of the aortic limb of the heart, p.c, 

 IVrii urdial cavity. PI, Dotted outline of pleural cavity. Rec, Rectum. Sc, Sub-cardinal vein, which is 

 derived from the cardinal and on the right side- of the body forms part of the vena cava inferior. Scl, Sub- 

 c lavian vein, six, Anlage of the superior longitudinal venous sinus, which is formed by the union of th- 

 veins, /..?., from the sides to make a single vessel between the r ( >r,.), r .,] ; ... ' .i er . i'ni.if, 



Right umbilical vein v, x Vena 



'>, Wo! (Viar. 

 of I lie n'glil and 



