RADIUM IRRADIATION AND DEVELOPMENT 143 
solutions. A series of these lesions is shown in figures 8, 9, and 10. 
Figure 8 shows a young rat with the dorsal integument partly 
dissected away, exposing a typical haemorrhagic area in the region 
of the frontal lobes. The slow development of this lesion could 
be easily noted through the thin, transparent scalp. This young 
was one of several treated in utero with 1350 mc.hrs. of gamma- 
ray radiation on February 21, 1920. It was born two days later, 
and died on March 38rd. The young rat shown in figure 9 was 
a litter mate of the previous animal. It shows the presence of 
three distinct haemorrhagic areas, a small frontal lesion, a fairly 
extensive one in the occipital region, and a small lesion in the 
subcutaneous tissues in the thoracic region, near the middorsal 
line on the left side of the body. This animal also died on 
March 8rd. _ A third animal belonging to the same litter is shown 
in figure 10. Here is seen a still more acute reaction, as shown 
by the fact that the animal died a day sooner than in the two 
cases above. There is an extensive area of meningeal haemor- 
rhage which covers most of the dorsal portion of the brain, 
involving the frontal and occipital regions and the medial area 
between, as well as a considerable portion of the right temporal 
area. In addition, a distinct, rounded haemorrhagic lesion may 
be noted on the reflected skin on the left side of the body. This 
lesion occurred in the midshoulder region of the back. 
The heads of several of the young rats showed marked lateral 
compression. In one case a haemorrhage so affected the spinal 
cord as to produce complete paraplegia. The tissues of these 
animals were studied histologically. Save for the mechanical 
disturbances produced by the presence of the extravasated areas, 
the most marked pathological conditions were seen in the liver 
and intestines. In the first case there was a pronounced fatty 
degeneration of the hepatic cells, and in the second, a desquama- 
tion of the lining cells of the intestinal mucosa. 
3. It is interesting to note that the other half of each litter 
survived the treatment, grew to a normal size, and some ani- 
mals have lived for over eighteen months. They showed the 
effects of the late uterine treatment by the following arrests in 
development: , 
