INFLUENCE OF ROENTGEN RAYS UPON METABOLISM 893 

 their destructive action increases with decreased wave length, although. 



O O 



more slowly than in the case of amylase. The actual percentage loss in 

 activity due to the action of rays less than 2800 Angstrom units is much 

 greater in the case of lipase than in the case of amylase. They could 

 observe no direct relationship between the absorption of ultra-violet rays 

 by pancreatic juice and their action on pancreatic enzymes. Pincussohn 

 noted that the protease activity of the blood of animals injected with a 

 fluorescent substance (eosin) was greater after exposure to light. The 

 rate of destruction of pepsin, trypsin, enterokinase, ptyalin, amylopsin, 

 and the pro-enzyme trypsinogen was reported by Burge, Fischer and Neill 

 to be proportional to the amount of energy applied. The active wave 

 length they used was between 0.302 M. and 0.297 \i. 



Metabolism in general is believed to be stimulated by light energy. The 

 experiments of Pettenkofer and Voit(a), Johansson, and Lehman and 

 Zuntz show that metabolism with complete muscular rest is slightly greater 

 during the day than at night. Zuntz was first to call attention to the 

 significant fact that even when perfect muscular relaxation ensues there 

 may be still influences such as light on the retina or sounds which may 

 act reflexly on the organism and slightly increase the metabolism. 



Cleaves who has reviewed the literature to 1.904 concludes that one 

 set of experiments apparently proves that light increases the oxygen 

 carrying capacity of the red blood cells and therefore influences oxidative 

 processes of the organism. Other experiments show increased output of 

 CO 2 when animals experimented on were exposed to light and this in- 

 crease was supposed to be due td stimulation of the protoplasm, prob- 

 ably due to both stimulation and the increased supply of oxygen. Adult 

 animals therefore fattened more easily in the dark as there is less 

 combustion. 



Rubner(a) remarks that while the radiant energy of the sun is large 

 in quantity, he has been unable to find any influence upon a man under 

 ordinary circumstances. Zuntz while living on the summit of a high 

 mountain of the Alps observed the basal metabolism increased as much 

 as 40 per cent and that exposure to sunlight was almost without effect 

 on the metabolism. Hasselbalch(&) found that if the naked body of a man 

 was strongly exposed to ultra-violet rays the rate of respiration was di- 

 minished while the depth was increased. The skin was red with dilated 

 capillaries and the blood pressure fell. Lindhard(a), in 1910, showed 

 there is a yearly periodicity of the respiratory rate in the Arctic region, it 

 being less in the spring and summer than in the winter. The enormous 

 variations in the chemical intensity of the sun's rays in the Arctic region 

 are undoubtedly the cause of this effect. The same phenomenon has 

 been observed by Lindhard(&) in Copenhagen. The volume of respiration 

 increases 25 per cent- in the summer but the intensity of metabolic proc- 

 esses are not affected. While these investigators noted that the ultra- 



