J. F. LOUTIT 



tumours in animals inoculated with cell-free extracts of tissue cultures stem- 

 ming from foreign tumorous mice. They are also similar to the conditions 

 reported by Hays et al.~^ and Latarjet-- who have apparently induced 

 tumours with foreign desoxyribose nucleic acid (DNA). In all cases the 

 foreign DNA or viral 'agent' is injected into animals whose nornial immuno- 

 logical mechanisms could be defeated owing to their own prematurity, by 

 supersaturation or by inactivation. 



Be that as it may there is still the incubation period and during this period 

 some progressive step- wise process could be operating and, to me, this seerr.s 

 a probable explanation of the delay no matter whether the initial act was 

 viral infection, genetic transformation or physico-chemical damage. 



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^Brown, VV. M. Court and Doll, R. Medical Research Council Special Report, Serial 



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DISCUSSION 



Dr. Hoffman: With regard to the tumour viruses and the virus-like particle aspects 

 of neoplasia, Bernhardt makes two points of interest. In an increasing number of 

 instances of tumours, in increasing numbers of animals or species there are particles 

 resembling viruses, which can be demonstrated microscopically. In a smaller number 

 of these cases it can actively be filtered and used to transmit neoplasia. The point 

 Bernhardt makes — that in the case of the fowl, in 12 per cent of apparently normal 



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