Physostigmine (I) and many of its analogs have been the subject of much study with regard to certain physiological properties which they. exhibit when introduced into the animal The phenyl carbamate nucleus has been shown to be the active group in the alkaloid. 2. Physostigmine and certain other phenyl carbamate derivatives strongly inhibit choline esterase. The constriction of the pupil of the eye (miosis) of the test animal when the ...