RADIUM IRRADIATION AND DEVELOPMENT 147 
DISCUSSION AND SUMMARY OF RESULTS 
It has been shown that when doses of radio-active solutions 
are injected into an animal marked physiological reactions take 
place. Large doses produce severe toxemia, resulting in pro- 
nounced pathological changes in the various viscera of the white 
rat (10). A study of metabolic changes in dogs, as determined 
by urine analysis, showed that, following intravenous injections 
of such solutions, there were very decided increases in the total 
nitrogen content of the urine, the urea, creatinine, uric acid, and 
the total phosphates (12). A prompt reduction occurred in the 
number of white blood cells of the dog after intravenous injections 
of these solutions, associated with a marked decrease in the 
relative percentage of circulating lymphocytes (13). In order 
to reduce as much as possible the severity of the reaction, very 
small doses of radio-activity were used in the experiments 
recorded in this article. But even with comparatively small 
doses, certain rats treated in utero showed very acute reactions. 
Many were killed by the treatment and were absorbed or aborted. 
Others were found showing pronounced areas of subcutaneous 
extravasations, mainly situated along the middorsal line of the 
body and within the meningeal sinuses. This condition was 
probably due to the destructive action of radium on the endothe- 
lium of the blood vessels, as well as a possible increase in blood 
pressure, as was shown to occur in the dog by Burton-Opitz and 
Meyer (14) after intravenous injections of very small quantities 
of radium bromide. A similar reaction of the blood vessels to 
radiation was previously reported by Halkin (15) for the skin of 
pigs, and by Danysz (16) for radiated mice. This destructive 
action of radium on the blood vessels is in line with clinical 
observations on the usual prompt regression of very vascular 
tumors (the angiomata, in particular) after exposure to irradiation. 
The changes in the rat embryos of this experiment are inter- 
esting in so far as they show that a sufficient amount of radio- 
activity was able to pass the placenta and subsequently affect 
the developing embryo. This occurred after subcutaneous as 
well as intravenous injections of the mother. By far the most 
