THE biogenetic origin of the tropane bases has recently been the subject of some discussion1,2, Mortimer1 suggesting that the tropane skeleton may be derived from the breakdown products of tryptophan metabolism. This novel idea is contrary to the accepted hypothesis that a base such as tropine is produced in vivo by reactions analogous to the in vitro synthesis3 of tropinone from succindialdehyde, methylamine and acetone. The succindialdehyde is considered to be a metabolite of ornithine, and James4 showed that significant increases in the amount of hyoscyamine in Atropa belladonna occurred following the feeding of arginine or ornithine.