294 



E. BOYLAND 



VOL. 4 (1950) 



shown with X-rays. Radiotherapy of cancer started (Grubbe^) soon after Rontgen's 

 discovery of X-rays. Seven years later Frieben^ reported that a skin cancer had devel- 

 oped in a man who had been exposed to X-rays. Muller* showed that X-rays increased 

 the incidence of mutations in Drosophila and Painter and Muller^ and Roller^ 

 found that X-radiation caused visible abnormalities in chromosomes. 



All these effects can be produced by certain chemical agents, such as the nitrogen 

 mustards and urethane, which for this reason have been called radiomimetic. The carci- 

 nogenic hydrocarbons such as 1:2:5: 6-dibenzanthracene are also radiomimetic agents. 

 Table I shows the grouping of the different effects. 



TABLE I 



REFERENCES TO EFFECTS PRODUCED BY X-RAYS AND BY CHEMICAL 

 COMPOUNDS WITH RADIOMIMETIC ACTIONS 



Another effect which many of these agents produce is the bleaching or greying of 

 hair. This was described in mice exposed to X-rays by Hance and Murphy^*. A similar 

 effect occurs with nitrogen mustard derivatives either aliphatic (Boyland et al^^) or 

 aromatic (Haddow et al.^^). This greying of hair is a permanent effect, remaining with 

 the mouse for the remainder of its life. It may be perhaps considered as a somatic 

 mutation and in this respect is analogous to an induced tumour. The change from col- 

 oured to white hair which is induced is unlikely to be due to selective survival of more 

 resistant white hair follicles as the skin of the black (C57) or agouti (CBA) mice used do 

 not appear to contain white hairs. This change of colour in a part of the body is a dis- 

 continuous variation in properties like the change of normal into cancer cells. Both 

 changes are brought about by the same agents which also induce germinal mutations. 

 References p. 300 . 



