The nerves of the iris, discovered by Petit1 and described by de Saint-Yves,2 have been the object of a great number of discussions, in regard to their existence, course and relationship with the other parts of the iris. The reason for these discussions is the lack of a staining method that gives consistent and uniform results and that is applicable to the pigmented iris of mammals. A review of the literature on this subject shows that our knowledge of the nerves of the iris is dependent on descriptions of the iris of albino rabbits and mice, or on incomplete studies on the pigmented iris. Furthermore, the results obtained by several investigators on the study of the naturally depigmented iris, depend on unreliable procedures.
In 1877, Pause3 employed a defective method, but one which allowed him to make a sufficiently accurate description of the more important nerve plexuses
BALADO M. A SATISFACTORY METHOD FOR STAINING THE NERVE FIBERS OF THE IRIS. Arch NeurPsych. 1926;16(4):442-446. doi:10.1001/archneurpsyc.1926.02200280050005