GENERAL ANATOMY OF EMBRYO OF 12 MM. 



237 



with the organs of the right side, but with two exceptions, first, the floor of the 

 pharynx is represented as if cut through considerably to the left of the median 

 plane; second, the heart is cut to the left of the median plane. The brain and 

 spinal cord are drawn as if opened to show the modeling of the inner surface of 

 the medullary tube. The pharynx is so drawn as to indicate something of the 

 modeling of its floor surface. The opening of the veins into the heart and of the 

 auricle into the ventricle, and the interventrieular orifices, are shown. Of the 

 digestive canal only the entoderm is represented, so that the figure displays the 

 entodermal walls of the oesophagus, stomach, and intestine, and shows the two 

 pancreatic anlages. Similarly only the entodermal portion of the trachea and 



Bu 



M 



Oe Tra IV 



III 



FIG. 173. PIG, 12 MM. SAGITTAL SERIES 7. WAX RECONSTRUCTION BY J. L. BREMER. 



Bu, Pharyngeal bursa. Hy, Hypophysis. M, Mouth-cavity. Oe, (Esophagus. Tra, Trachea. I, II, III, IV, 

 Gill-pouches, developed as lateral pouches of the pharynx. X 40 diams. 



lungs is included, -and the same is true of the caudal end of the Wolffian duct 

 and of its outgrowth, which forms the anlage of the kidney. The same is further 

 true of the gall-bladder, of which only the epithelial portion is represented. In 

 this figure the arterial system is fully displayed. The pulmonary artery and the 

 aortic trunk are completely separated. A small artery from the pulmonary arch 

 to the lungs is included, and the figure shows the entire system of branches from 

 the main aorta. 



Figure 175 is in many respects similar to figure 172, and is intended to show 

 chiefly the disposition of the veins. There are also included in this figure the 

 Wolffian body and its duct. The pharynx and the heart are supposed to have 

 been cut through, well to the right of the median plane. This makes it possible 

 to indicate in the figure the origin of the pulmonary aorta and of the true aorta. 

 The following are the most important veins: the umbilical, which passes around 

 the umbilical opening and en f 2rs the liver; the portal vein, which receives the 



