2 J 8 
Williams.—Observations on the Action 
Section I. Changes produced in Cells of Saxifrage 
UMBROSA BY X-RAYS. 
1. Historical survey. 
2. Nature of the X-ravs, factors to be considered. 
3. Methods used. 
4. The series of changes produced. 
5. Summary. 
1. The general interest aroused by the discovery of X-rays by Rdntgen 
in 1895 led to the action of these rays on various plant and animal structures 
being studied at an early date. There are many conflicting statements in 
the work of the earliest workers, which is only to be expected when one 
considers the fact that the actual nature of the rays was then unknown and 
experiments could not be carried out under any standard conditions. 
In 1897 observations upon Vallisneria spiralis under the radiation 
from a ‘ gas bulb ’ were published by Lopriore ( 2 ). This observer found 
that treatment for thirty minutes produced an acceleration of circulatory 
rate, but there was a return to the normal rate when the radiation ceased. 
Treatment which lasted one hour caused the protoplasm to become yellow, 
granular, and coarsely vacuolated, while after two hours of radiation, 
although the cells were still living and the protoplasm circulating, the 
chlorophyll bodies were becoming colourless. The suggestion of stimula¬ 
tion implied by the acceleration of circulation is supported by the fact that 
other workers increased the rate of opening of buds by exposing them to 
X-rays, while it is well known from the medical side that small doses of . 
radiation may accelerate cell division of tumours in animals. 
Although Lopriore did not reach the stage in which cells were actually 
killed while under the radiations, lethal actions were soon discovered during 
work on animal cells, and Schaudinn ( 3 ) found that treatment for fourteen 
hours caused amoebae to round themselves off. It was found that many 
bacteria were peculiarly resistant to these rays, although so powerfully 
affected by ultra-violet light. 
Meanwhile analogous experiments were being made upon cells exposed 
to radium, and although these will be dealt with in a later paper, attention 
must here be called to the work of Packard ( 4 ), because he suggested that 
the presence of chlorophyll increased the resistance of the cells, and that the 
presence of light was a factor of importance in his tests on chlorophyll- 
containing cells. 
2. It has now been established that X-rays are waves of the same type 
as light waves but of much shorter wave lengths than those of either visible 
or ultra-violet light. 
