24 



SCIENCE 



[N. S. Vol. XXXVII. No. 940 



rest. In Entomological News, 1908, p. 458, I 

 gave reasons for thinking that A. calif arnica 

 deserved subgeneric rank ; Mr. Walker's re- 

 sults appear to support this idea, and even 

 suggest the question whether it should not be 

 generieally separated, taking with it several 

 related forms. 



Certainly Mr. Walker's book should be in 

 every biological laboratory, both as an example 

 of good taxonomy and as a useful work of ref- 

 erence, ^shna being common nearly every- 

 where. 



T. D. A. COCKERELL 



University of Coloeado 



SPECIAL ARTICLES 



A PRELIMINARY NOTE ON THE COAGULATION OF 

 PROTEINS BY ULTRAVIOLET LIGHT 



In order to gain some insight into the action 

 of ultraviolet light on living cells it became 

 necessary to study its efPect on certain constit- 

 uents of protoplasm. Attention was first 

 given to proteins and a series of experiments 

 were made with egg-white, egg albumin and 

 ox-serum. 



1. Experiments with Egg-white. — Fresh 

 egg-white was cut up with scissors and placed 

 in a quartz tube, at room temperature, 10 cm. 

 from a quartz mercury-vapor lamp. The tube 

 was completely filled and stoppered. After 1 

 or 2 hours a feathery coagulum began to form 

 in the tube upon the wall nearest the lamp. 

 This coagulum increased in amount, and after 

 35 hours the tube was quite full of a flocculent 

 coagulum. There was a peculiar strong odor. 



Fresh egg-white was diluted with an equal 

 amount of distilled water. The solution be- 

 came opalescent from the precipitated glob- 

 ulin. The tube was exposed at room tempera- 

 ture in the same manner as the tube contain- 

 ing the undiluted egg-white. There was a 

 similar coagulation, but it was more abun- 

 dant. There was also the same peculiar odor. 

 In this case the coagulum slowly settled as it 

 formed. The solution, therefore, was clearer, 

 and there may have been a better penetration 

 of the light. In another experiment the pre- 

 cipitated globulin was filtered out before ex- 

 posure. Fifteen hours after filtering, the so- 



lution was still clear. On exposure to the 

 light a fine sediment was formed which slowly 

 settled to the bottom of the tube. The char- 

 acteristic odor was present. 



In all the experiments described above con- 

 trol preparations in glass tubes, exposed in the 

 same manner, and at the same temperature, 

 gave little or no coagulum, and none of the 

 characteristic odor. The coagulum formed in 

 the quartz tubes, whether they were open or 

 closed. It formed equally well in tubes which 

 had been connected with the air-pump and 

 pumped out so as to remove the dissolved air. 

 No bubbles of gas were formed during the ex- 

 posure, nor could gases be detected in the so- 

 lution by pumping with the air pump after 

 the exposure. 



2. Experiments with Crystallized Egg-al- 

 humin. — Crystallized egg-albumin was pre- 

 pared by the method described by Hopkins and 

 Pinkus. The egg albumin was recrystallized 

 seven times. The ammonium sulfate which 

 came down in the last crystallization was not 

 dialyzed out. Solutions were prepared con- 

 taining 1, 2, 5, 10 and 20-per-cent. of the al- 

 bumin. All were exposed in quartz tubes at 

 room temperature. The 5-per-ceiit. solution 

 gave the most coagulum and in subsequent ex- 

 periments with crystallized albumin 5 per 

 cent, solutions were used. Coagulation was 

 much more rapid in the crystallized albumin 

 plus the ammonium sulfate, than in the fresh 

 egg-white. 



3. Experiments with Crystallized Egg-al- 

 humin Dialyzed Against Tap Water. — Albu- 

 min freed from ammonium sulfate by dialyzing 

 against tap water coagulates very readily 

 when exposed to the light at room tempera- 

 ture. It may be sensitive to longer wave- 

 lengths than the fresh egg-white, since con- 

 siderable coagulum forms in the glass tubes. 

 A quartz and a glass tube were exposed at 

 room temperature for 15 hours. The quartz 

 tube became opalescent and then opaque with 

 a finely divided coagulum which did not settle, 

 but which could be thrown down with a centri- 

 fuge. A feathery coagulum formed in the 

 glass tube on the side nearest the lamp. This 

 increased in amount, until the tube was filled 



