934 



BIOLOGICAL EFFECTS OF RADIATION 



B 



r-O- 



1 

 Vv 



AB 



R 



which is being used for the measuring of weak corpuscular radiation, 

 alpha and beta rays, and very extensively in work with cosmic radiation. 

 The counter (Fig. 3) consists of a metal tube which serves as cathode; 

 through this tube a special wire is stretched which is held in position by 

 means of rubber stoppers. This wire is connected with a high resistance 

 through an electrometer with the ground. The cathode is connected to a 

 set of batteries (about 1000 volts) and grounded through a resistance. 

 The tube is filled either with air or some other inert gas at reduced pres- 

 sure. The setup is balanced so that only ionization of the gas in the 

 tube will permit a discharge to take place. Radioactive material in the 

 laboratory, or cosmic radiation will cause a certain number of discharges 

 f^^ to take place. Rajewsky covered the 



wall with a photoactive material, 

 cadmium, since it is photoactive in 

 the short ultra-violet, and equipped 

 the tube with a quartz window. The 

 cell when protected with a heavy 

 iron jacket gave about 30 discharges 

 per min. as recorded by visual obser- 

 vation or by means of a mechanical 

 5^^ 7^. recording device. When he placed 



Fig. 3. — Diagram of Geiger-MuUer some of the mitogenetic senders before 



counter. A, counting chamber; B, in- ,-, . ^ r j.u j. au j* 



sulating stopper; AB, batteries; E, ^he wmdow of the COUnter, the dlS- 



electrometer; R, resistance; D, anode charges increased about 30 per Cent. 



wire. fter ajewa y, .) jj^ ^^^^ observations with the sender 



for 10 to 12 min., and then for 10 to 12 min. without the sender, 

 or with a sheet of glass placed between sender and cell. Repeating 

 this for several hours he obtained results that are very interesting, A 

 typical set of records is given in Table 3. 



Rajewsky was not able to obtain any effect from yeast, the most 

 generally used of all the senders. Up to the present Rajewsky has not 

 published any statistical evaluation of his results. The work of Rajewsky 

 was quickly followed by that of Frank and Rodionow (79) ; the latter work- 

 ing with the same type of setup were able to verify the work of Rajewsky. 

 Frank's results were very striking. However, the work could not be 

 repeated at will, since the cathode quickly declined in its ability to emit 

 photoelectrons, and for every experiment they were forced to prepare a 

 new counter. Thus the work was very tedious and was robbed somewhat 

 of its reliability. Frank and Rodionow found that the emission was very 

 much increased by the presence of visible light at the sender, but they 

 were careful to keep the visible light from the counter by means of a 

 spectrograph and used only the ultra-violet part of the spectrum. 



Siebert and Seflfert (269) report in a short notice that they have been 

 able to construct a set of two modified counters which have exactly the 



