RADIUM IRRADIATION AND DEVELOPMENT 145 
disturbance in brain development, the skull was found to be 
asymmetrical, narrow, thicker than normal, and concave in the 
frontal region. 
Figure 12 shows a dorsal view of a normal, untreated brain of 
an adult rat, magnified five diameters. In figures 13 and 14 are 
dorsal and lateral views of a brain of oneoftherats which belonged 
to the same litter as those of section 2 of this series. ‘This animal 
was treated with 1350 me.hrs. on February 21, 1920, was born on 
February 23rd, and was killed December 31, 1920. This was one 
of the animals which (except for blindness) showed no abnormal 
neurological reactions. The magnification in figures 13 and 14 
is the same as that for the control brain in figure 12. The dorsal 
view in figure 13 shows an apparently normal cerebellum and 
normal olfactory lobes, but the part of the brain which represents 
the rudiments of the hemispheresshowsa great lack of development 
of cortical substance. In a side view of the brain in figure 14, 
the cortex may be seen to be very thin; indeed, not completely 
covering what should normally be the frontal, occipital, and 
lateral aspects of the brain. The remains of the hemispheres do 
not sufficiently approach each other in the median line to cover 
the colliculi beneath. In figure 13 the meninges on the left side 
of the brain have been removed, but on the other side they have 
been left in place. It was possible in this specimen to see the 
lateral ventricles through the transparent membranes. Several 
other brains have been studied which showed various degrees 
of developmental arrests resulting from radium treatment. In 
some cases the hemispheres were markedly reduced in size, were 
widely divergent in the median line, and yet the pallium was 
complete over the entire surface. In all these cases there was 
marked optic atrophy. These brains are now being sectioned, 
and a study of them in greater detail will be the subject of a 
separate communication. 
e. A histological study of the eye showed that the eyeball was 
reduced to one-fourth the normal diameter. The retina was 
missing, but traces of the choroid remained as a few scattered 
pigment cells. The cornea was three times as thick as normal 
and covered with four or five layers of opaque squamous epithe- 
