RADIATION AND RESPIRATION 



1065 



depressant effect of X-rays on respiration, especially if the doses are as 

 great as 5 H.E.D. 



Radium Radiations. — Except for the slightly absorbed gamma rays, 

 the radiation from radium compounds is entirely different in nature from 

 light, ultra-violet, and X-rays, yet it must be considered for its possible 

 influence on respiration, partly because of its natural occurrence to some 

 extent. Of the other two types of radiation — the alpha and beta 

 particles — the former is so completely absorbed by the glass containers 

 of the radium salts that its effects arc not involved in the ordinary use of 

 radium and are there- 

 fore considered else- 

 where in this report. 

 The beta particles are 

 left as a possible factor 

 in the exposure of plant 

 tissue to radium. 



For evidence of the 

 relation of these parti- 

 cles to respiration we 

 have a few series of 

 tests in which suitable 

 observations were taken 

 and conclusions drawn, 

 but it is very difficult to 

 compare these results 

 and to reach a general 

 conclusion as to the 

 effect on plant respir- 

 ation. The variations 

 in the sources of the 

 radiations, the degree of absorption in the several cases, the dis- 

 tance between source and tissue, the organ and species of plant 

 used, the length of exposure, the time between exposure and measure- 

 ment of effect, etc., are so great and their bearing on the data so important 

 that only qualitative statements can be made here. Briefly stated, the 

 effect of beta particles appears to be a lowering of the rate of respiration 

 more or less in proportion to the length of exposure except for a temporary 

 acceleration of the rate if the exposure is very short. 



The first study of the influence of radium on respiration was reported 

 briefly by Hebert and Kling (5) in 1909. They found a marked depres- 

 sion in the rate of respiration of lilac leaves, at least if the leaves showed 

 injury from the exposure. Both O2 and CO2 changes were measured, 

 but the data were given for only a very few experiments. 



The next test of the action of beta particles was made by Redfield and 

 Bright (16) who used vmsoaked radish seeds and measured their CO2 pro- 



Hours 



Fig. 2. — Root tips of Vicia Faba; graphic represen- 

 tation of rate of respiration afte"* radiation with X-rays 

 at 1 H.E.D. Time in hours after irradiation is shown as 

 abscissas and rate of respiration compared with the control 

 (100) is shown as ordinates. Dotted lines represent 

 averages of the probable error. {After Bersa, 1.) 



