Letter from Norman Heatley, Merck and Co, Rahway, New Jersey to Howard Walter Florey, Oxford Pleased that Florey got good results with corn steep liquor - cylinder assay method for penicillin leaves much to be desired - discusses setting up of replicates - mentions other work on assay techniques - Kemball Bishop and Pfizer are distinct enterprises - Merck and Squibb are using 'Oxford units' - calling them 'Florey units' - hears that the NRC are initiating a search for other mould and bacterial products - gives details of a case at New Haven treated with penicillin - having technical difficulties with penicillin at Merck - Dr Raper has identified Oxford mould as Aspergillus flavus. 21 March 1942