ULTEAVIOLET LIGHT MEIER 355 



photographs of cancer tissue taken 5 minutes after the death of an 

 animal, and those of the same tissue taken 3 hours later show a 

 marked change in the microabsorption spectra of the cells. 



By irradiating and photograjahing with ultro violet light in regu- 

 lar sequence, Dr. Francis F. Lucas of the Bell Telephone Laborato- 

 ries has made series of photographs that show tlie cunudative effects 

 of irradiation on the cells of blue-green algae. He has also made 

 photomicrographs of living cells from malignant growtlis. 



Paramoecia, 1-celled microscopic animals, have proved a favorite 

 subject for experunentation in the ultraviolet. The lethal effect of 

 the rays is preceded by a stinmlating effect, according to Weinstein 

 (1930). Kentschler (1031) describes the destruction of paramoecia 

 in great detail, beginning with a shortening of the cell, the separa- 

 tion of the two cell walls to form a blister, the coagulation of the 

 proteins of the cytoplasm, and finally the breaking of the cell wall, 

 which allows the coagulated cytoplasm to flow into the surrounding 

 liquid, where it disintegrates. The moving pictures made by the 

 Cancer Research Laboratory show these changes in both paramoecia 

 and Euglena. 



Ultraviolet light has also been used by Kohler (1904) for making 

 microphotographs of living Nostoc, an alga, and bacteria at 2800 

 A and 2750 A, respectively. Wyckoff and Arian (1931) have made 

 ultraviolet microphotographs of bacteria also. 



The destruction in the ultraviolet of yeasts, tiny colorless micro- 

 scopic cells, so valuable because of their ability to make ferments, 

 is not effected as quickly as that of bacteria, probably owing to 

 the larger size of the yeast cells, De Fazi (1921) reports that the 

 Peroni Brewery in Rome has an ultraviolet plant for the sole pur- 

 pose of freeing the yeast from bacteria. Two yeasts that were 

 producing spoilage in a carbonated beverage were destroyed in a 

 short time by ultraviolet light, according to Feuer and Tanner 

 (1921). 



Lindner (1923), using a bottom-fermentation brewery yeast, 

 greatly increased the velocity of the fermentation of dextrose by 

 exposure to ultraviolet rays. Thus fermentation of 30 grams of 

 dextrose yielded 199 cubic centimeters of carbon dioxide in 24 hours, 

 and under irradiation by ultraviolet the yield was 2,743 cubic centi- 

 meters of carbon dioxide. The exposure of the yeast cells under 

 fermentation conditions favored the activity of the yeast, but the 

 exposure of the cells in a shallow layer of liquid was fatal. 



Because of the bactericidal action of these ultraviolet rays, it is 

 possible to make use of them in the sterilization of large quantities 

 of water. During this process a complete destruction of animal 



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