“The acetylation of sulphanilamide by pigeon liver extracts was found to be markedly inhibited by amides of salicylic, 5-bromosalicylic, 5-methylsalicylic, and 6-aminonicotinic acids, and by hydrazides of benzoic, salicylic, 4-aminosalicylic, nicotinic , and isonicotinic acids, as well as by p-aminosalicylic acid.”