BIOLOGICAL EFFECTS OF RADIATIONS 701 



by increasing molecular motion. This results in a local rise in tem- 

 perature. At low temperatures the chemical activities of a living 

 organism are slowed to such an extent that extremes will produce 

 death. A physical factor in causing death by freezing is the forma- 

 tion of ice crystals which disrupt the cellular structure of the tis- 

 sues. Biological processes are accelerated by increases in tempera- 

 ture and, within limits, the activity may be doubled by each 10 

 degrees (centigrade) increase in temperature. If, however, the 

 temperature becomes too high biological processes are retarded and 

 even death may result. Physical factors associated with death re- 

 sulting from high temperature are loss of water, inactivation of 

 enzymes, oxidation, and coagulation of the protoplasm. 



High Frequency Oscillations 



Hertzian (radio) waves are longer in wave length than the infra- 

 red radiation. They apparently are not biologically effective under 

 usual conditions of radio transmission, but high frequency oscilla- 

 tions of shorter wave lengths applied across two terminals at a 

 high intensity will subject the intervening material to an immediate 

 rise in temperature. This "internal heat" is being used in the 

 treatment of certain diseases in which fever aids the body in fight- 

 ing the infection. The physiological action is the result of electrical 

 stress. It has been found to destroy certain bacteria (in milk, for 

 example), to increase germination of seeds, and to produce abnor- 

 mal development of certain embryos. 



Effects of Ultraviolet Radiation 



The radiation contained in sunlight whose wave length is too 

 short to be visible is the ultraviolet. It may be produced by mer- 

 cury arc or mercury vapor lamps. Small amounts of ultraviolet 

 radiation retard growth of bacteria, protozoa, and fungi. Con- 

 tinued irradiation may cause the death of the organisms. There is 

 evidence that ultraviolet radiation increases the permeability of 

 cells. Proteins are altered chemically by long exposures to the 

 radiation. 



The importance of certain fish oils in the treatment of rickets has 

 long been recognized. Likewise, the importance of sunlight is not 

 a new discovery. A great step, however, was taken recently when 

 it was discovered that certain inert substances could be activated 

 by ultraviolet radiation so that they would function, as cod-liver 



