(112) Baer referred to Pokels' article in the journal 

 "Isis" (13, 1825) . Baer himself also published a small 

 article on a case of the underdevelopment of swine embryos 

 "Schadelund Kopfmangel an Embryonen von Schweinen aus der 

 fruhesten Zeit der Entwickelung besbachtet" (Nova Acta 

 Acad. caes. Leopold. Carol. Nat. Curios., 13, S. 829-835, 

 4°) . This report is interesting not because of its factual 

 side as it is based on the description of badly preserved 

 fetus, but because Baer passed through it to an important 

 conclusion: that acephilia can arise not due to the damage 

 of already- formed head, but as a result of the absence of 

 its primary rudiment (450) . 



(113) This anatomical article cannot be elucidated 

 here in detail. It is sufficient to point out its most 

 important conclusions. The comparative investigation of 

 structure of placentae in different mammals, including man 



as well, led to the following classification of these organs. 

 Baer distinguished four types of placentae: 1) placentae, 

 only adjacent to the maternal placenta, — a) continuous, 

 belt- like (in swine) and b) placenta divided into many 

 parts— cotyledons (in ruminants) ; 2) placentae, combined 

 with the maternal, — a) surrounding the fertilized ovum by 

 a belt (in Carnivora) and b) occupied one of its ends (in 

 man) . On the basis of a thorough study of the way of blood 

 vessels, Baer confirmed, that he never found passage of 

 vessels of mother to the ovum. In the adjacent combined 

 placentae, the vessels go beside each other, so that the 

 maternal vessels are distributed in that part of placenta, 

 which is directly connected with the chorion, and the vessels 

 of the fetus, on the contrary, only enter the mass adjacent 

 to the placenta. 



About the mechanism of gas exchange and nutritional 

 substances between blood, flowing in maternal vessels, and 

 blood, moving in the vessels of the fetus, Baer, — as he put 

 it — "could not form any opinion" (450) . 



(114) The influence of Baer affected the university 

 programs of that time. At Petersburg University, the 

 history of development of animals within 30 and 40 years was 

 read by Stevan Semenovich Kutorgaya (1808-1861), the 

 brilliant lecturer, who attracted in his lecture room students 



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