A NEW CUTANEOUS NERVE-FIBER CONNECTION WITH THE FRONTAL NERVE IN THE FROG RANA-ESCULENTA - A MORPHOLOGICAL-STUDY

The frontal nerve arises from the frontal organ, which represents the extracranial component of the pineal complex in some lower vertebrates , and interconnects the frontal organ with the epiphysis and the brain . The existence of a previously unreported nerve branch of the frontal nerve is described here in the frog Rana esculenta and called the lat eral nerve. The course of the lateral nerve and its junction with the frontal nerve have been consistently detected by means of different te chniques: toluidine blue staining in semithin sections, the Landau-Ign esti method for myelinated nerve fibers, the methylene blue intravital staining for peripheral nerves, and in vitro tracing with the carbocy anine Dil. A method to preserve intact the delicate lateral nerve duri ng dissection is also described. The lateral nerve was consistently fo und to be unilateral, and to join the frontal nerve at one end (either on the left or the right side), whereas the other extremity was found to be dispersed in the dermis. Thus, the lateral nerve could represen t a new pathway interconnecting the skin and the brain and/or the fron tal organ in the frog.