RELATIVE POSITIONS OF THE WHITE AND GRAY COMMUNICATING RAMI / 解剖学报

ABSTRACT

The rami communicantes in five adult cadavers were examined.All the rami were taken down serially in three cadavers;each pair was cut transversely into two parts to be separately sectioned and treated by the Weigert-Pal and Ranson's pyridine silver methods.Their components were observed under microscope for the presence or absence of the myelin sheath in order to identify a filament as of white or gray ramus. On the thoraco-lumbar levels,the shallower or lower ramus was coarser of the pair and its junction with the respective spinal nerve was also farther from the corresponding intervertebral foramen.It was composed mainly of myelinated fibers and hence designated as the white ramus.On the other hand,the deeper or upper member of the two was relatively slender and its junction with the pertinent spinal nerve was nearer to the foramen.This branch contained chiefly unmyelinated fibers and represented the gray ramus.The oblique ramus,which occurred occasionally and consisted mainly of myelinated elements,was also clas- sified with the white ramus. The White rami were definitely distributed from thoracic 1 to lumbar 3.The gray rami of the cervical 6-8 and lumbar 4-5 also contained a number of mye- linated fibers and even some sympathetic cells were aberrated into them.The upper cervical and lower sacral gray rami contained but rarely any myelinated elements. Thus,the white and gray communicating rami were formed not purely of myelinated or unmyelinated fibers,but a mixture of both,with,however,the predominence of one kind.In general,it is possible to ascertain the relative positions of the two rami in a cadaver under dissection.