From the trunk bark of Aspidosperma polyneuron there was isolated normacusine-B (XIVi) and a new alkaloid, polyneuridine, the constitution (XlVa) of which could be established by mass spectrometry, n.m.r. measurements and eventual chemical conversion to normacusine-B (XIVi). Polyneuridine, therefore, is the C-16 epimer of akuammidine (XlVk), which in turn is identical with rhazine. The mass spectra of indole alkaloids related to yohimbine and ajmalicine exhibit certain characteristic peaks to which assignments have been made through the use of deuterated and other substituted indole alkaloids, ß-Yohimbine has thus been identified as one of the constituents of A. eburneum. © 1962, American Chemical Society. All rights reserved.