RADIUM PREPARATIONS AND METHODS OF EXPOSURE 83 



shown that, " a distribution of the radiating matter over a thousand 

 times its original volume has no appreciable influence on its radio- 

 activity." 



An illustration of some of the radium preparations used in the 

 following experiments is given in figure 2. See also Experiment 

 40, p. 147, and Experiment 42, p. 149. 



For the purpose of observing under the microscope the effect of 

 radium rays on individual living protoplasts, the writer ^ has devised a 

 radioactive microscopic slide, the preparation of which has been per- 

 fected by Mr. Lieber. This slide has been described as follows : 



"A solution of any desired concentration of radium bromide of 

 known activity is made in a suitable solvent, and applied to the sur- 

 face of the slide near the center. When the solvent evaporates a 

 film of the salt remains on the slide. The film is protected by a 

 coating of a specially prepared substance. Living cells may now 

 be mounted as on an ordinary slide, and their response, if any, to 

 the stimulus of the rays observed. The coating has the advantage, 

 not only of being sufficiently transparent to light, but easily trans- 

 parent to the /? and y rays, and in less degree to the a rays also." ^ 



The methods of applying to living plants the various preparations 

 here described are explained in detail in connection with the experi- 

 ments. It may be mentioned here, however, that in no case has the 

 radium salt been permitted to come into contact with the plant, nor 

 with any portion of it. The effects produced are due solely to the 

 action of the rays coming from either the radium bromide direct, or 

 from the radioactive emanation. 



Bibliography 



1. Gager, C. Stuart. Radium in biological research. Science, N. S. 25: 



589. 1907. 



2. Lieber, Hugo. Radium and some methods for its therapeutic appli- 



cation. Am. Med. 9: 72. 1905. 



3. . Improved methods for applying radium. Jour. Soc. Chem. 



Indust. 24. 15 Mr 1905. 



4. . A new and possibly improved method of using radium. Arch. 



Rontgen Ray 9 : 253. 1905. 



5. . Radium and its use in therapy. Homoeop. Eye, Ear, & Throat 



Jour. July, 1907. (Separate reprint. ) 



6. Rutherford, E. Does the radio-activity of radium depend upon its con- 



centration.'' Nature 69 : 222. 1904. 



