when administered orally, unless accompanied by a mono- 
amine oxidase inhibitor (6). The tryptamines—especially 
N, N-dimethyltry ptamine—are the active constituents 
of hallucinogenic snuffs of South America (2, 6, 18, 22, 
27) prepared from Anadenanthera peregrina (yopo), 
A. colubrina (huilea) and Virola thetodora and probably 
other species (yakee, epend, nyakwana, paric’) (22). Yet 
the narcotie vinho de yurema, prepared from the roots of 
Mimosa hostilis (11), the active constituent of which is 
N, N-dimethyltryptamine, is extremely active when 
taken orally. It has furthermore recently been learned 
that the two common admixtures of the ayahuasca, caapi 
or yajé drink prepared basically from bark of either Banis- 
teriopsis Caapi or B. inebrians, rich in harmala alkaloids, 
are leaves containing N, N-dimethyltryptamine: Banvs- 
teriopsis Rusbyana (1, 6, 16) and Psychotria psychotriae- 
folia (7). There is no question but that the addition of 
leaves of Psychotria psychotriaefolia and especially of 
Banisteriopsis Rusbyana very strongly enhances the color 
visions, increases the intoxication and prolongs the nar- 
cotic effects of the drink. In the case of these two ad- 
mixtures, it is clear that, when added to a beverage 
containing the harmala alkaloids, harmine and harmaline, 
they would be in the presence of monoamine oxidase 
inhibitors. As has recently been suggested, ‘*. . . perhaps 
this fact, coupled with the presence of small amounts of 
related isomers, may help account for the effectiveness 
of the crude preparation. . .”’ or ‘‘perhaps the strong 
concentration of active principles or the presence of other 
unidentified substances facilitate absorption”’ (6). 
In the instance of yurema, which is prepared appar- 
ently from the roots of Mimosa hostilis with no admix- 
ture whatsoever, a monoamine oxidase inhibitor might 
possibly be present, but we do not yet know. With the 
orally administered Virola-resin of the Witotos, one 
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