266 Applied Biophysics 



case and connected to the high-tension generator by means of 

 shock-proof cables. This permitted the tube to be freely moved 

 with respect to the generator. In recent years, particularly with 

 super-voltage X-ray equipment, operating at voltages of 1 million 

 volts or more, there has been a reversion to the scheme of 

 enclosing the tube and generator in a single earthed metal tank. 

 Reduction in the size of the apparatus has been achieved 

 by using freon gas *' or air under high pressure -^ as the in- 

 sulator. 



Incidentally, the shielding of high-tension parts has led to 

 improvements in another aspect of safeguarding the health of 

 X-ray workers. It had early been observed that workers in 

 X-ray departments complained of headaches and exhaustion, and 

 of inflammatory conditions of the respiratory tract. These effects 

 were attributed to nitrous fumes and ozone, generated by brush- 

 discharge from sharp angles and points on the high-tension 

 system. Subsequent experiments indicated that such effects as 

 irritable cough, exhaustion, and blood changes occurred if the 

 ozone content of the air exceeded 0.5 milligram per cubic centi- 

 meter. It was concluded that the eft'ects observed in X-ray 

 workers bore a great resemblance to the symptoms of ozone 

 poisoning. Clearly, the introduction of shock-proof systems, 

 with the consequent elimination of brush-discharge, led to a 

 further improvement in working conditions. 



International Recommendations 



At the first international congress of radiology, held in London 

 in 1925, the question of international agreement on the main 

 principles of protection was discussed. Three years later, at the 

 second international congress, held in Stockholm, the British 

 Committee submitted its recommendations as a basis for agree- 

 ment, and these were accepted with but few changes. The Inter- 

 national Commission ^'^ stated that its recommendations were 

 designed to "deal only with the more essential matters involved, 

 minor questions of detail being left to each country to elal^orate. 

 The question of seeking legal authorization for such recom- 



