478 BIOLOGICAL EFFECTS OF RADIATION 



Ewing (96) points out that "the enormous swelhng and hyper- 

 chromatism of the epitheUal nuclei after large doses of radium is a strictly 

 specific feature of cell damage from irradiation which has never been 

 satisfactorily explained." This damage may cause increased permea- 

 bility of the cell membrane, resulting in an increased ability to absorb 

 water. The most pronounced changes are those occurring in blood 

 vessels, "of which the external evidence of the initial hyperemia followed 

 by induration and relative anemia bear simple witness. The initial 

 hyperemia seems to be merely a somewhat peculiar inflammatory process 

 with vasodilation, exudation of serum, leucocytes, and, especially after 

 roentgen rays, red blood cell infiltration." 



Permanent epilation or loss of hair may follow massive doses of 

 roentgen or gamma rays. Pressure anemia reduces the dosage required 

 (89, 305). The hair which grows again after moderate doses is often 

 devoid of pigment (13, 15, 249, 250). But when irradiation is given by 

 the fractional method, very large doses can be tolerated (342, 403). The 

 hair of rabbits which had received 5600 r by the fractional method grew 

 again with no apparent injury. Only after doses of 9600 r was epilation 

 permanent. The effects are the same whether the fractional doses are 

 given at a high or a low intensity. 



Skin lesions produced by Grenz rays having a wave-length of 4 to 8 A 

 are not unlike those which follow exposure to ultra-violet and roentgen 

 radiations (45, 108, 275, 276). The erythema may appear within 12 to 

 72 hr. and increase in severity (313). With further exposure the skin 

 becomes progressively less sensitive and may fail to respond even to 

 large doses. Pigmentation may last as long as 10 months (307). 



A comparison of the effects of very low voltage roentgen rays with 

 those produced by cathode (11, 189, 318) or ultra-violet rays shows that 

 the latter are much less effective than the more penetrating radiations 

 (237). The erythema dose for 12-kv. roentgen rays lies between 80 and 

 120 r, but as the voltage is decreased, the number of roentgens required 

 to produce this reaction rises, until at 4 kv. it is 1000 r (275, 395). 

 Expressed in terms of energy, the roentgen ray erythema is about 300 

 erg/cm.- For cathode rays it is about 500 erg/cm. 2, but very much 

 larger doses result in only a mild reaction not followed by pigmentation 

 or epilation. In comparison, Coblentz states (43) that the erythema dose 

 for ultra-violet waves (2790 A) is 500,000 erg/cm. 2, and for 2800 A it is 

 1,500,000 erg/cm.2 Other effects of cathode rays are discussed by 

 Pape (264). 



Carrie (35) sensitized mice with hematoporphyrin and obtained an 

 epilation with less than the normal epilation dose of Grenz rays. Not 

 only was the time of onset shortened, but the reaction was neither as 

 severe nor as lasting as that produced by high doses of Grenz rays alone. 

 This effect resembles that produced by ultra-violet radiation rather than 

 that of roentgen radiation. 



