Karl E. Mason 



403 



induced during the removal and rupture of implantation sites, on closer ex- 

 amination proved to be associated invariably with fetuses which had just died 

 or with those whose continued survival could be considered questionable. In 

 all subsequent bio-assay tests for vitamin E (in which positive responses are 

 based upon the presence of two or more viable fetuses at the sixteenth day 

 of pregnancy) implantation sites containing dead or living fetuses have been 

 routinely examined with the aid of a dissecting microscope. The intact sites 

 were placed in warm physiological saline, the state of circulation in the yolk 

 sac noted, the fetal membranes carefully removed, and the fetus with its at- 

 tached umbilical vessels and placenta examined grossly. The location and 

 extent of vascular injury in each fetus, and the relative position of the latter 



TABLE 2 

 The Frequency of Vascular Changes in Dead and Live Fetuses at the Sixteenth Day 



* This number includes only rats in which one or more of the living fetuses showed vascular changes. 



t Autolysis was so far advanced in many of the dead fetuses that no evidence of the vascular damage remained. 



in the uterine horns, were recorded. The data of table 2 present the incidence 

 of vascular changes observed in 210 rats possessing one or more viable and 

 affected fetuses at autopsy on the sixteenth day. 



Vascular Changes in Fetuses at the Sixteenth Day 



The earliest changes observed consisted of dilation and congestion in super- 

 ficial blood vessels. Vascular plexuses in the region of the cranial vault, 

 external ear, shoulder, and dorsolateral portions of the trunk were most fre- 

 quently involved. In the capillary bed related to these plexuses there often 

 were petechia-like areas of variable size and shape which, under high magni- 

 fication, appeared to represent localized areas of extensive capillary dilation 

 and stasis. The gioss appearance of normal fetuses is shown in plate 1, figure 1 . 

 The injected specimen shown in plate 1, figure 2, illustrates the character of this 

 vascular congestion in superficial plexuses of the supraorbital, posterior au- 

 ricular, and shoulder regions, and in more localized areas on the limbs and 

 lateral body wall. The dark color of the latter is due to retained blood, for the 

 ink suspension usually failed to penetrate these larger areas of vascular stasis. 

 The plexiform dilations and petechiae usually appeared in the venous chan- 

 nels, whereas the more extensive areas of hemorrhage to be described later, 

 involved also the arterial trunks and their capillary bed. However, it was 

 often impossible to determine which division of the vascular system was con- 

 cerned. Although normal circulation could be observed in vessels immediately 

 adjacent to the affected areas, as well as elsewhere, the volume of blood was 



