CONGDON: EFFECTS OF RADIUM ON LIVING SUBSTANCE.— II. 367 
the nerve cells themselves degenerate quickly when free from necrosis 
of the blood vessels and from hemorrhage. 
It was found possible in Cambarus to bring a small radium cell, 
without a groove, but otherwise similar to that used for Allolobophora, 
into direct contact with the ganglia of the ventral nerve cord. In 
this way the intensity of the beta rays which fell upon the ganglia 
was known, because there was no absorption of them by intervening 
tissues. In order to prevent the cord from being injured by possible 
earlier degeneration of the tissues surrounding it, the treatment was 
made short but intense. 
In each experiment one to three ganglia of the ventral nerve cord 
of two animals were exposed by removing some of the abdominal 
sclerites. The opening was made just large enough to accommodate 
a small radium cell containing thirty milligrams, of radium one 
thousandth as strong as pure radium bromide. A dummy cell of 
the same size and shape was used for the control animal. It was found 
possible to apply the cell to the cord with little bleeding. The ani- 
mals were kept motionless by tying abdomen and caphalothorax to a 
board. A slight current of water was allowed to pass over them to 
permit respiration. Especial care was taken to prevent pressure or 
other mechanical disturbance to the cord. Immediately upon the 
conclusion of an exposure, the condition of the tissues about the cord 
was noted. The ganglia were then immediately removed and fixed 
in 95 % alcohol, after which they were stained in toluidin blue and 
erythrosin to differentiate the Nissl flakes. 
Pure radium bromide was applied in one experiment for eighteen 
hours. Four animals were exposed in succession, each for twenty- 
four hours, to the cell of weak radium and another to ten milligrams 
of very pure bromide contained in a glass tube. There was no necro- 
sis produced by the rays in either ganglion cells or fibre tracts. The 
Nissl flakes, because of their promptness in responding to various 
forms of nervous injury, were examined carefully for peculiarities of 
any kind. They did not differ from those in unexposed ganglia of 
animals treated in a similar way with a dummy cell. 
As it is the common experience of dermatologists that exposures to 
intense beta rays produce degenerative effects in a very short time, 
and since the Nissl flakes show injury so quickly, it is not likely that 
the ganglion cells in these experiments were fixed during a latent period 
precedent on degenerative change. The same cell of weak radium 
used for these exposures produced a marked effect upon frog embryos 
in the yolk-plug stage within forty-eight hours after exposure. 
