PATHOGENESIS OF MALFORMATIONS IN CHICK EMBRYO WITH EXPERIMENTAL HEMORRHAGE

Experimental hemorrhage produces various alterations in chick embryos of 48 hours. Some of these alterations are generalized, e.g. delay of development or hyperchromophilia of all the cells. Other alterations are localized, as malformations of the axis of the embryo. Two factors are responsible for the appearance of localized malformations: the phase of development and the blood supply. The regions of the embryonic axis which are in a sensitive phase during the hemorrhage are: the somites 17 to 22, and the primitive streak and tail bud. One or two pairs of somites between the 17th and 22nd are affected in all the cases. Usually they are smaller than their neighbours, and sometimes, when the normalization of the circulation is too slow, fusion of the somites can be observed. In 3-day old embryos, the primitive streak shows numerous round cells, when in a further stage form a necrotic islet. Together with the sensitive phase, the deficient circulation in the caudal region is responsible for alterations of the tail. The circulation troubles are caused by the slow advance of the aorta in caudal direction and by the small calibre of this artery in the caudal region. © 1969 Springer-Verlag.