480 BIOLOGICAL EFFECTS OF RADIATION 



roentgen radiation because with a low alkali reserve epilation may be 

 produced by a dose of 300 r, while with a normal reserve, 600 r must be 

 given to produce the same effect. He thinks that shorter wave-lengths 

 require higher dosages to elicit the same amount of reaction. 



When radiations are combined with other injurious agents, the effect 

 on the skin is a summation of the effects of each agent acting alone. 

 Hawkins (141) exposed the skin of a guinea pig to 30-kv. roentgen rays, 

 without filter, and to heat (46°C). The only reaction produced by these 

 agents acting alone was a swelling of the tissues; a combination of the 

 two, however, induced a well-marked and persistent damage. The 

 results were the same regardless of the sequence in which the agents 

 were applied. 



So also when roentgen rays are combined with ultra-violet radiation 

 the result is an intensification of the dermatitis caused by the former (259). 

 This experiment was performed in the hope that the ultra-violet might 

 have an ameliorating effect following accidental overdosage with roentgen 

 rays. There appears to be no antagonistic or reversal effect in the com- 

 bination of ultra-violet and infra-red rays (47). 



The epilation dose has been proposed by many observers as a biological 

 unit of measurement, but the reviewer believes that it is unsatisfactory 

 because of the variability in response among different animals in a group, 

 and because the degree of epilation is difficult to determine. The 

 epilation dose for rabbits has been estimated to be 1000 r (302), 2000 r 

 (124), while Warren has found that the erythema stage of Miescher's 

 classification of epilation stages (228, 231) is produced by 2000 to 2400 r. 

 Perhaps a more careful study with definite quantities of radiation may 

 serve to remove this uncertainty in dosage. 



The effect of roentgen and gamma rays on the reparative processes 

 which follow simple incision has been investigated. Takahashi (347) 

 iound that young capillaries and fibroblasts are very sensitive, their 

 growth being stopped by a 5-min. exposure to beta and gamma rays 

 from 15 mg. of radium (0.2-mm. Ag filter). A 30-min. dose so injures 

 the tissues that regeneration is induced from nearby structures. He 

 found no evidence of stimulation. It should be emphasized that the 

 proliferation following large doses is a regenerative process and not 

 the result of stimulation. Pohle, Ritchie, and Wright (278) exposed the 

 skin of rats before and after incision to doses of 1000 r, using wave-lengths 

 of 0.34 and 0.18 A. This treatment had no effect on the healing process 

 unless it was given less than two days after incision, in which case it 

 retarded healing. But Fukase (109, 110) states that doses of 400 r on the 

 incised skin of rabbits favor the reparative process. 



Some careful work which takes into consideration the dosage-time 

 relations between irradiation, injury (incision), the lethal dosages for 

 the cells concerned with the repair process, etc., might give interesting 



