482 BIOLOGICAL EFFECTS OF RADIATION 



Connective-tissue cells and the endothelial cells are very resistant to 

 in vitro autolysis after irradiation in vivo (372). This fact might suggest 

 that severe damage to the endothelial cells is not a primary factor in the 

 capillary dilation which develops in the skin during the production of an 

 erythema, but rather that some other mechanism is responsible for the 

 fluctuation in the size of the capillaries. An investigation of this problem 

 would be well worth undertaking because it may not only lead to further 

 information about the function of the capillary control mechanism but 

 would also establish more definitely the changes brought about in the 

 capillary by radiation. 



Miescher (227, 229, 235, 238) has described in detail the color changes 

 in the human skin after roentgen radiation of various wave-lengths. 

 His doses are uncertain but the quantities are comparable with each 

 other, in minimal and maximal ratios of 1:6 and 1:8. He lists seven 

 stages; (a) sUght reddening, (5) weak reddening, (c) strong reddening, 

 (d) very strong reddening with a slight cyanotic overcast, (e) reddening 

 and swelling of the whole field, (/) reddening with vesicle formation and 

 desquamation, and {g) ulceration. In addition, he determined a pig- 

 mentation scale. The pigmentation was distinguished from the redness 

 by observing the skin under compression through a glass plate, and was 

 divided into 4 degrees from "slight" to "very strong." 



He found three waves of reaction in the skin, the "time" border of 

 which for the first wave lay between the first and fourth day, for the 

 second wave, between the eighth and the twenty-second day, and for 

 the third, between the thirty-fourth and the fifty-first day. The greatest 

 intensity occurred during the third wave. In some instances no isolated 

 third wave was observed, while in a few cases a fourth wave appeared. 

 The latent periods between the individual waves are not related to the 

 dose but seem to be influenced by individual factors. In the same 

 individual the rhythm of the curve of redness is the same for both large 

 and small doses. 



In the course of the erythema reaction the timing of the pigmentation 

 curve showed considerable variation from the waves of reddening, but 

 in general each wave of redness was followed by one of pigmentation. 

 Sometimes there were more of the latter than of the former (198). It 

 has been thought that the blond skin is more sensitive than the brunette, 

 but probably it is not. A mild erythema is more readily visible in a pale 

 skin. The child skin, in general, shows the same fluctuations as the 

 adult skin (224, 303). 



SchaU (319) found a sharp reaction of redness from 4 to 8 hr. after 

 roentgen radiation. This immediate response lasts for 24 hr. or more. 

 The erythema is maintained at a high level for the whole period of 75 

 days, but there are two major waves centering around the thirty-fifth 

 and the sixtieth days, as Miescher found. The pigment begins about 



