then blood reaches the heart through the descending and 

 ascending veins. Pander described the terminal sinus, and 

 the blood flow in this network. 



Turning to the digestive tract, Pander remarked that 

 the stomach on the third day is already an elongated form, 

 narrowing anteriorly in the direction of the esophagus. 

 Posteriorly, it has an opening corresponding to the heart 

 depression; the borders of the opening continue posteriorly 

 into the intestinal folds. The mesentery above the stomach, 

 which previously consisted of two layers, now becomes a 

 single layer. The posterior intestine has the form of a 

 cone, with an anterior opening. The body wall, surrounding 

 the cone of the colon, represents the rudiment of the pelvis, 

 which forms by connection with the peritoneal folds. From 

 the pubis, the blastoderm turns to the spinal surface of 

 the fetus. The rudiment of the true amnion is still unclosed 

 above the middle of the back. Along the border of this part, 

 the serous membrane continues in the blastoderm. In a 

 footnote Pander mentioned Tredern's mistake of considering 

 this continuation as the amnion. He noted later that the 

 formation which he called the "false amnion" is not identical 

 with that which Wolff designated by that name. In the 

 posterior part of the embryo, Pander indicated the presence 

 of a lentil-sized cavity which is filled with a transparent 

 fluid; it originates from the surface of the colon and holds 

 the umbilical artery. This cavity, Pander said, is usually 

 called the chorion, and Oken compared it with the mammalian 

 allantois. Pander's observations of development of the liver, 

 lungs and kidneys at this stage correspond with Wolff's 

 descriptions. 



Section 12 concerns the embryonic characteristics after 

 four days. The yolk membrane is exhausted and falls behind 

 the blastoderm; the blastoderm surrounds almost all the yolk. 

 Arteries and veins are filled with more intensely colored 

 red blood. In the vascular membrane the arteries are 

 accompanied with the corresponding veins. In the auricle 

 it is possible to see an interceptor in the form of two half- 

 rings, i.e. the beginning of the separation of the left and 

 right auricles. The left is larger than the right and always 

 contains drops of blood seen through its wall. In the 

 ventricle a separation is also observed: above the aortic 

 bulb a reddish oval hillock develops which is situated across 



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