RADIUM IRRADIATION AND DEVELOPMENT 151 
which were associated with the acute reactions. Also, if the 
effect was largely due to vascular disturbances, from the nature 
of the radiation employed, one would expect more generalized 
changes throughout the entire brain. However, on the other 
hand, Craigie (20), in his recent paper on the relative vascularity 
of various parts of the central nervous system of the albino rat, 
suggests that ‘“‘the vascularization of the more recently evolved 
centers (of the cortex cerebri) is more susceptible than the more 
ancient regions to sexual, hereditary or environmental influences. ”’ 
From a neurological point of view, it is interesting to consider 
that the animals with practically no cerebral cortex reacted so 
normally in their ordinary behavior. Except for blindness, there 
was no other apparent sensory disturbance, and motor coordina- 
tion appeared perfect. The physiological functions localized in 
the cerebral cortex of the rat were in these animals apparently 
transferred to the basal ganglia and other paleokinetic portions 
of the brain, showing the remarkable degree of compensation 
possible in the mammalian brain when the disturbing element 
acts at an early period in its development. In this connection 
it is worth mentioning that the radium emanation did not produce 
a sudden traumatic effect, as is normally the case with the experi- 
mental production of brain lesions, and, in fact, the radium 
changes were probably prolonged over a considerable pericd. 
This condition favored the establishment of compensatory 
reactions, and exists (as shown by the writer in a recent article 
(21)) even in the ease of radium lesions experimentally produced 
in adult mammalian brains. 
The reproductive system completes its development a consid- 
erable time after birth, and so it is not at all surprising that 
these structures should have shown a considerable amount of 
atrophy due to the developmental arrest during the prenatal 
period. The ovaries and testes appeared to suffer with equal 
severity. 
An interesting correlative relation was shown by the fact that 
the other viscera (digestive, excretory, ete.) of the animals that 
showed marked developmental arrests of the nervous and repro- 
ductive systems were apparently normal and the animals grew 
