The Pharmacology of the Pigeon Pupil

The avian ciliary body and iris contain striated muscle rather than smooth muscle. Only reptiles share this unique feature.1Both Boehm and Iske reported successful mydriasis in birds with local curare2,3; however, Wood obtained no mydriasis with either local curare or atropine, but he did report modest success with local nicotine.4Presumably the oculomotor nerve controls the pigeon pupil, because stimulation of the oculomotor nerve, ciliary ganglion, or ciliary nerve causes miosis, while stimulation of the cervical sympathetic ganglia and fibers has no effect upon the pupil.3This study was performed as an attempt to clarify the pharmacology of the pigeon pupil. Materials and Methods The common pigeon, Columba livia, was used. Representative skeletal muscle relaxants, parasympatholytics, sympathomimetics, and surface-active agents were selected. Five pigeons (10 eyes) were used for each drug except nicotine, in which case only 2 birds (4 eyes) were used. Two to