Letter from H E Holling, Medical Research Council, Clinical Research Unit, Guy's Hospital, London SE1, to Henry Barcroft Would like to arrange 'a simultaneous demonstration of plethysmography' but had planned to show his apparatus at the next meeting of the Medical Research Society - does not think that Shepherd will wait. Suggests that Barcroft go ahead and show at the London meeting. Thinks that Shepherd's apparatus will be most useful for investigation of peripheral vascular disease. 1 May 1947