Phrenic nucleus of gibbon

Abstract

The phrenic nerves of ten gibbons (Hylobates lar) were cut unilaterally. The animals were sacrificed from 7 to 33 days postoperatively. The cervical segments of their spinal cords were embedded in paraffin. Transverse sections of 40 and 10 micra in thickness were prepared from 5 and 3 spinal cords respectively. Coronal sections of 40 and 10 micra thick were made from each of the rest. The sections were stained with 0.1 percent toluidine blue 0 solution. The phrenic columns were found from the level of the third to the sixth cervical segments of the spinal cords. In the third and fourth cervical segments of the spinal cords, the phrenic nucleus could be found in three positions; (i) dorsal to the ventrolateral cell group, (ii) in the central part of the venral grey column, and (iii) between the ventrolateral and the ventromedial cell groups. In the fifth and sixth cervical segments, the phrenic nucleus was only found in the last position. The neurons of the phrenic nucleus were medium-sized and small-sized cells, all of which showed chromatolytic change. The phrenic columns had a beaded appearance.