Mammalian Embryos. 



185 



have proceeded to some extent before the radium was applied. 

 The remnants of the embryos were small, nodular bodies attached 

 to the placentae (figures were shown) and had lost all resemblance 

 to properly developed fetuses. 



In one case a small, ovoid shaped sac was found, attached by 

 a thin stalk to the uterine wall (figure shown). This apparently 

 represented the remnants of a former embryo and placenta, 

 although neither one could be recognized any longer. In the 

 sac extravasated blood and cell detritus were found. A great 

 many large cells of an epithelioid nature probably belonged to 

 the former embryonic syncytium. The wall of this cyst was 

 formed by fibrous connective tissue. 



In a number of other cases (group II), the fetuses were not 

 killed by the radium emanation, but peculiar macroscopic lesions 

 appeared in their skin vessels. 



When the fetuses were removed from the uteri, peculiar hemorr- 

 hagic areas were noticeable, in some cases just along the dorsal 

 midline, in other cases, spreading over the entire body with the 

 exception of the ventral surface. These extravasations took place 

 in the vessels of the subcutaneous connective tissue and along 

 the meningeal sinuses. In all cases, one or more hemorrhages 

 appeared in the midline, mainly in the head and thoracic region. 

 It seems that the vessels in this dorsal median zone are especially 

 liable to injury. In one instance, there was a large area of hemor- 

 rhage extending over the thoracic and lumbar region. Its outline 

 was just symmetrical to the dorsal midline (figure shown). In 

 other cases, a great number of such hemorrhagic areas, some 

 extremely small, were found over the lateral aspects of the head 

 and body. Probably these affected fetuses would have died, if 

 left longer in the uterus, and would have undergone absorption. 

 In many animals which we killed in the early parts of the experi- 

 ments we failed to find any fetuses, although we definitely believed 

 that these animals had been pregnant before. We probably waited 

 too long after treatment, so that the embryos were completely 

 absorbed, when the animals were opened. 



Not all of the fetuses of one litter are affected in the same degree. 

 In one case, for instance, we found among 7 fetuses 3 showing 

 hemorrhagic lesions, 2 beginning to macerate and 2 in the process 



