Dawson et al. (1) have shown that the pyridine ring of nicotinic acid is utilized to form the pyridine ring of nicotine in sterile cultures of tobacco root. Since studies with animals and some microorganisms have demonstrated that tryptophan is converted to nicotinic acid (2)) tryptophan might reasonably be expected to yield the pyridine ring of nicotine. However, experiments have shown conclus...
