EADIATION-INDUCED BONE TUMOURS 157 



Kember, N. F. (1960). J. Bone Joint Surg. 42B, 824. 



KuzMA, J. F., and Zander, G. E. (1957). Arch. Path. 63, 198. 



Lisco, H. (1956). CIBA Foundation Symposium on Bone Structure and Metabolism, p. 



272. 

 Taylor, D. M., Sowby, F. D., and Kember, N. F. (1961). Phys. Med. Biol. 6, 73. 



DISCUSSION 



BENSTED: I should Very much like to support these ideas but also suggest that we pay 

 more attention to the idea that some of these results may be explained in terms of the 

 greater volume of bone tissue which is being irradiated as a result of fractionating a dose 

 of ^^P. I feel that some further investigations on these lines might be fruitful. 

 CURTIS: I want to enquire about the experiments with ^^P. You mentioned that as you 

 gave a smgle dose, the metaphyseal region is irradiated and with the next dose you 

 irradiate a different region and so on. But is it not true that as the plate moves up, it does 

 so by the division of cells which are lower down? So that the second dose I would say, is 

 being given to the progeny of cells which have originally been irradiated and so on. Is 

 this right? 



LAMERTON: This may indeed be true. In fact, it is very difficult to talk about the actual 

 radiation dose given to any population of cells since there is migration of cells within the 

 tissue certainly as far as bone is concerned. 



CURTIS: So that the two-event phenomenon we spoke of yesterday would certainly hold 

 for the ^^P experiments if not for the X-ray experiments? 



LAMERTON: Yes, tliis is one explanation of the ^^P experiments. But we should have liked 

 to have found the difference in response with the fractionation of the external radiation 

 but this did not turn out to be so. 



glucksmann: With regard to the significance of damage, I think you ought to distinguish 

 between the types of damage present. Have you looked for vascular damage? This type 

 of damage may be crucial. 



bensted: We have thought about vascular damage as a strong possibUity in the phos- 

 phorus experiments but we haven't done the appropriate experiments. In this context I 

 might perhaps quote the experiments of Jee and his co-workers at Utah on dogs with 

 thorium, plutonium and radium burdens. They made a study of the micro-circulation 

 in the bones of these dogs by the technique of India Ink injection. As a result they were 

 able to show that there was impairment of the circulation to the Haversian system. They 

 have some rather pretty pictures of the trabecular surface of the bone separated from 

 the capillary by quite a thick layer of fibrosis. They concluded that the death of osteocytes 

 was certainly due to the disturbance in the vascular suppl3^ Tliis disturbance in the local 

 environment might weU also influence the behaviour of the connective tissue in this 

 region. 



muller: To add to what Dr. Curtis had to say, I think one might raise another question 

 in connection with fractionation and that is whether the repeated dosing would not 

 result in a wider distribution of the damage, that is to say the cells at the end would be 

 cells which had received the whole dose of repeated appUcations either in their ancestral 

 cells or m themselves, whereas they would have left behind a trail of other cells deeper 

 down which had also received a good deal more than which the cells in the corresponding 

 position would have received as a result of a single dose. 



lajnierton: I think this is quite possible. Dr. MuUer. The trouble is, we know so little 

 about the migration of cells in a growing bone. Dr. Kember has done some work with 



