148 HALSEY J. BAGG 
interesting observation concerned the presence of lesions similar 
to those described above in rat embryos whose mother was 
treated with radio-active solutions a considerable time before 
mating. The writer has no explanation to account for this 
phenomenon. It would appear that the treatment of the mother 
several days previous to conception has lessened the faculty of 
the later-developing embryo to form proper endothelium of the 
blood vessels, and the wide distribution of these lesions over the 
body of the embryo (peculiar to this group of animals) would 
tend to substantiate this view. One female was injected twenty- 
two days before fertilization, and since the solutions lose their 
radio-activity very rapidly (there is about a 50 per cent reduction 
in the first hour after the preparation) the likelihood of any 
radio-activity remaining over during this period and affecting the 
egg at a later critical moment is remote. The amount of radio- 
activity remaining after twenty-two days, if present at all, should, 
as determined from physical computation, beinfinitesimally small. 
The series of intravenous injections again emphasize the 
specific action of radium emanation in the production of typical 
areas of subcutaneous emtravasations in the developing young, 
and in addition shows that the placenta may act in the nature of 
a ‘shock absorber’ and prevent the embryo from receiving the 
full effect of the radiation. 
We now come to a consideration of the cases wherein pregnant 
females were treated with external applications of comparatively 
large doses of gamma-ray radiation. At this time a report is 
given only for embryos treated towards the end of pregnancy. 
The writer plans to continue this line of investigation and treat 
at earlier prenatal periods. 
The results emphasize the well-known delayed reaction asso- 
ciated with gamma-ray radiation. There was approximately a 
ten-day interval following treatment during which no changes 
were noted in the embryo, and during this period the young 
animals were born in an apparently normal condition. Acute 
reactions promptly occurred at the completion of this time, 
killing half of each litter. The young rats died showing typical 
radium changes, such as anemia, diffuse edema, and meningeal, 
