the originally existing ventricle. This is the foundation 

 of the right ventricle. From the aortic bulb, closely 

 adjacent to the ventricle, two or three branches go out, 

 and from their base the aorta is formed, which later is 

 bent in the form of an arch. The amnion is only slightly 

 open and includes the whole fetus, which already has 

 rudiments of the legs and wings. The peritoneal folds, 

 which by bending back form the actual amnion, spread along 

 the sides of the fetus, and near the region of the heart 

 and around the borders of the pelvis constitute the borders 

 of the chest and abdominal cavities. The opening of this 

 cavity is the rudiment of the umbilicus. 



These observations, which were completely novel, can 

 only suggest that Pander's contemporaries could not under- 

 stand those features they discovered. Such misunderstandings 

 were displayed not only by Oken, but even by Baer, to whom 

 Pander tried to explain his observations. In his auto- 

 biography (p. 212) Baer reports: 



Pander had performed his investigations for some 

 months, and I requested that he give me an idea 

 of the method by which the closed body develops 

 from a flat rudiment. Apparently, Pander had at 

 that time a complete, and obviously a correct, 

 idea about that. I remember well that he ran for 

 the assistance of a handkerchief, spread it on 

 his hand, and by bending the fingers tried to give 

 me a visual idea of the formation of the gizzard. 

 But the process remained unclear to me, perhaps 

 because I could not, as I think now, clearly 

 imagine the formation of the intestines. 



The subsequent formation of the internal organs Pander 

 described as follows. The stomach is completely closed; it 

 goes into the duodenum to the extent that it is the duodenum 

 rather than the stomach that opens in the regions of the 

 former heart depression. From the duodenum, the middle 

 intestine begins to form. It is at that time composed of 

 two layers, joined at the dorsal borders, which continue 

 into the mesentery. The peritoneal borders of these layers 

 are still separated and extend along the sides into the 

 vascular and mucous layers of the blastoderm. The lungs are 

 located near the heart; they have the shape of extremely 



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