Two Unifactorial Characters for which Man is Polymorphic

IT has been recognized for many years that humans excrete methanethiol (methyl mercaptan) after eating asparagus, and it has been assumed that this character is universal^1,2. We have found, however, that while some subjects excrete detectable amounts of methanethiol after ingesting only three or four sticks of asparagus, no significant amount of the compound appears in the urine of others after ingestion of as much as a pound of asparagus. Biochemical investigations of this metabolic difference are being made in collaboration with Dr. P. W. Kent. Nencki's¹ identification of the odorous substance in urine as methanethiol has been confirmed by isolation of the corresponding silver mercaptide.