RADIUM IRRADIATION AND DEVELOPMENT 141 
injected directly into the blood stream through the caudal vein. 
This was six times greater than the usual dose in the first twoseries. 
Three young were born dead twenty-four hours later. They 
showed very definite radium changes, typical of those already 
recorded for the subcutaneous series. Figure 6 shows a foetus 
still attached to an apparently normal placenta, but a characteris- 
tic area of extravasation was found over a considerable portion 
of the left side of the head. In figure 7A a dorsal view shows 
another embryo with two comparatively small haemorrhagic 
areas along the dorsal midline, and the placenta in this case is 
also normal. The third foetus in this litter was apparently 
normal, but the placenta (fig. 7B) had acted in the nature of a 
‘shock absorber’ in protecting the foetus from exposure to the 
radio-activity, and it was so swollen and completely filled with 
blood as a result of its injury, that it had the appearance of a 
large haemorrhagic sac. 
Series B. Results from radiating nearly full-term pregnant rats with 
gamma-ray radiation 
Ten rats were treated at the end of about nineteen days of 
pregnancy. It was found that exposure to about 1350 mc.hrs. 
of radium emanation was sufficient to produce very decided 
changes in the embryo and yet leave the pregnant females suf- 
ficiently uninjured to be able to nurse their young and care for 
them until after the weaning period. When the dose was 
increased to 3378 me.hrs., the young were severely injured, and 
were either killed outright or died two or three days after birth. 
The following are the conditions that resulted in the first 
generation of animals treated in utero with a dose of about 
1350 mce.hrs.: 
1. The young of each litter were born two or three days after 
the treatment, alive and apparently normal. 
2. About ten days after treatment, about half of each litter 
became markedly anemic, showed symptoms of diffuse edema, 
and promptly died. There was an easily recognizable slow 
development of meningeal and spinal-cord haemorrhages, similar 
to those already described as a result of treatment by radio-active 
