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DISCUSSION 



Latarjet: I would like to add a comment to Dr. Loutit's paper. It 

 seems to me that at the present state of our knowledge there is a critical 

 question which concerns this 50 days: does the proliferation of homo- 

 logous or even heterologous material still occur at 50 days because the 

 immunity is still down, or does it occur because a state of tolerance has 

 been established by adding this homologous material when the im- 

 munity has been broken down? If we were to wait longer, could we 

 reach a state where full immunity has been recovered and the homo- 

 logous cells still occur, or not ? Do total body irradiations transform an 

 adult into a newborn animal? 



Loutit: I think it is probably a bit too early to be dogmatic; but at any 

 rate we have had some of these homologous animals from our previous 

 work as long as eight months after receiving homologous tissue, and at 

 eight months after receiving homologous tissue they will still take 

 tumours specific to the donor and not the host. Main and Prehn's skin 

 graft work was of about the same duration. I think the foreign skin 

 graft survived up to 190 days. 



Hollaender : Our mice have received rat bone marrow; we have quite 

 a number now which have been kept for 160 days, the erythrocytes are 

 still full red. What usually happens is that about 50 per cent die 

 between 30 and 60 days, another 25 per cent apparently get some kind 

 of a disease. The 25 per cent which then survive seem to be as per- 

 manent as we can have (this work has been done by Dr. Makinodan in 

 our laboratory). 



Haddow : Do you know the cause of death ? 



Hollaender: The first 50 per cent probably died because they finally 



