314 RETROGRESSIVE CHANGES 



portion of the spectrum that is most active in destroying bac- 

 teria, Whether oxidative processes are the cause of death in 

 animal cells is not known, but we are familiar with many 

 chemical reactions of various sorts that are initiated or checked 

 by the action of light. 1 Thus, bilirubin is oxidized into bili- 

 verdin, when acted upon by sunlight, even when not in contact 

 with air ; many vegetable oils are oxidized by sunlight, and it 

 is probable that the oxidizing action of light upon organic 

 compounds is of wide-spread occurrence. It is, therefore, 

 quite possible that such oxidative changes may be the cause of 

 necrosis produced by the action of light rays. 



x-rays produce necrosis which is peculiar in that an in- 

 terval of several days, or even weeks, may elapse after the ex- 

 posure before the necrosis manifests itself. Ellis, 2 who has 

 studied the literature, considers that the amount of necrosis is 

 out of proportion to the changes in the vessels, which some 

 have believed to be the cause of x-ray gangrene, and therefore 

 that the cells must be directly injured. 3 That x-rays have a 

 marked effect on metabolism has been abundantly established. 

 According to Musser and Edsall, 4 the effect of x-rays upon 

 metabolism is unequalled by any other therapeutic agent, and 

 is manifested by excessive elimination of the products of pro- 

 teid destruction, which arise particularly from the lymphatic 

 structures. 5 These changes have been studied, therefore, par- 

 ticularly in connection with the treatment of leukemia (q. v.). 

 The renal epithelium seems also to suffer injury in some cases. 6 

 Radium, which shares with x-rays the power of causing tissue 

 necrosis, does not have a similar effect upon the blood, nor do 

 the ultra-violet rays (Linser and Helber 7 ). 



The long-continued action of x-rays upon the skin has, in 

 many cases, led to the formation of cancer, apparently because 

 the proliferation stimulated by the rays progresses until it ex- 

 ceeds normal bounds. 8 



As the metabolic changes produced by x-rays indicate an 



1 See Davenport, " Experimental Morphology," 1897, p. 162. 



2 Amer. Jour. Med. Sci., 1903 (125), 85. 



3 Allen (Jour. Med. Kesearch, 1903 (9), 462) states that protozoa and 

 vinegar eels are killed by long exposure to x-rays, whereas plants are decidedly 

 stimulated in their growth. 



4 Univ. Penn. Med. Bull., 1905 (18), 174. 



5 A peculiar selective action for the generative cells is also shown by oxrays, 

 which cause marked atrophy of the ovaries and testicles. (See Albers-Schon- 

 berg, Munch, med. Woch., 1903 (50), 1859; Frieben, ibid., 1903 (50), 2295; 

 Specht, Arch. f. Gyn., 1906 (78), 458 ; Thaler, Deut. Zeit. Chir., 1905 (79), 576. 



6 See Schulz and Hoffman, Deut. Zeit. f. Chir., 1905 (79), 350. 



7 Deut. Arch. klin. Med., 1905 (83) 479. 



8 See review by Wyss, Beitr. z. klin. Chir., 1906 (49), 185. 



