Dr. LeRoy -2- May 28, 1951 This shows a definite relation of the lose to the exposure intensity. The major problem at present is to construct individual lids for every cage and fasten lids securely. To have one lid for 6 cagea, which has to be lifted to feed the animals, is a constant grave hazard since the identity of the animals is only marked om the cage. The individual lids will be completed and attached within « few days. We note that for Since this would like to set this in the very near We propose: (A) reasons of expediency 250 SV controls were onitted. mean relatively little supplementary expense, we should up here if animals of the same stock are still available future. To expose batches of 125 mice af ome sex at 2 dose levels below the LD-50 and keep ome batch of unexposed mice for controls. {B) For the cataract series ve should like to mtch every other station with an equal number of animls exposed here to Z rays, calculating tho dose on LD basig. This would mean the sddition of 600 to 1,000 mice to those already here. If this plan meets with your approval, would it be possible to arrange breeding of these animals at Bethesda and send then to us immedietely after weaning? Sincerely yours, JACOB FURTH oF: jd ec: Dr. McCrady Dr. Tolbert Dr. Langham br. Cronkite DO’ ARCHIVES