Copy letter from Herbert Rix, to John Newport Langley, Fellow of the Royal Society 'Dear Sir, I have resuspended Mr Sherrington's certificate in accordance with your request, but cannot make the addition which you ask to make. No alteration or addition can be made to a certificate after it has been signed. A new certificate must be taken out if it is required to add to the "qualifications" Yours truly Herbert Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 7 October 1891