DEGENERATION CHANGES AFTER UNILATERAL LUMBAR SYMPATHECTOMY, WITH GENERAL OBSERVATIONS ON THE NERVE-FIBRE CONSTITUTION OF PERIPHERAL NERVES AND NERVE-ROOTS

¹ Physiological Department, Queen's University of Belfast

(1) Following section of the preganglionic fibres passing to the subjacent ganglion the cells were found to show slight regressive changes at an early period following the lesion; but at later periods no differences could be observed between the cells on the operated and those on the normal side.

(2) After the same operative procedure the ganglia (seventh lumbar and first sacral) showed complete disappearance of the intercellular preganglionic plexus. This plexus was unaltered after section of the ventral roots at this level. The sympathetic outflow is therefore not segmental at this level.

(3) In the lumbosacral sympathetic chain sufficient myelinate postganglionic fibres were found to account for the majority of myelinate fibres in the grey rami. In these rami no myelinate fibres were found passing from the ventral or dorsal roots into the sympathetic chain. (4) The following points regarding the nerve-fibre constitution of peripheral nerves have been observed as a result of sympathectomy and lesions of the nerve-roots:—

(a) Sympathetic fibres in peripheral nerves are amyelinate.

(b) The small myelinate fibres which occur in main peripheral nerves in groups arise in the dorsal root ganglia and pass mainly to skin branches, but also to a lesser extent to the muscle branches.

(c) The small myelinate fibres which occur irregularly throughout a main peripheral nerve-trunk are ventral root components and pass entirely to muscle branches.

(d) There are amyelinate fibres in main peripheral nerves which arise in the dorsal root ganglia. These are always found associated with the groups of small myelinate fibres. They pass mainly to skin branches, but also, in smaller numbers, to muscle branches. They are less numerous than the amyelinate fibres of sympathetic origin.

(e) The amyelinate fibres of sympathetic origin travel in peripheral nerves either free among the larger myelinate fibres, or intimately associated with groups of amyelinate and small myelinate fibres from the dorsal roots. The sympathetic fibres to the skin are more numerous than those to muscle.

(5) No evidence has been found in support of the view that there are efferent fibres in the dorsal spinal nerve-roots. All fibres in these roots, both myeinate and amyelinate, appear to have their origin in the spinal ganglia.

(6) No changes were found in voluntary muscle at different periods after sympathectomy, even in young puppies during the active period of growth of the muscles.

The above investigations were carried out under the direction of Professor T. H. Milroy, to whom my best thanks are due for his criticism and advice.