Studies on the phrenic nerve and diaphragmatic plexus in rabbits and gerbils.

Studies on nerve fibres within the phrenic nerve and in the diaphragmatic plexus were carried out in one species, the gerbil, a small desert rodent. The resistance of this small mammal to surgical insult enabled experimental intrathoracic transection of the phrenic nerve to be carried out so that the results in 10 animals could be observed within the diaphragmatic plexus, the phrenic nerve, and the phrenic nucleus. The findings in the diaphragmatic plexus and in the nerve trunk strongly resemble corresponding results for other animals with regard to `persisting' fibres. The phrenic nucleus, however, is much more extensive in this mammal than has been found in any other species; it is represented within the second to sixth cervical segment, its rostral extremity occupying the intermediolateral part of the spinal grey matter. The possible functional significance of these findings is discussed in the light of the mixed functions of the diaphragm, either voluntary or involuntary.