REGENERATION OF THE PERIPHERAL VAGUS

Abstract

1. Recovery of the cardiac fibres of the vagus has been obtained in 12 rabbits, 5 cats, and 1 dog, the vagus nerve having been cut or crushed in the mid‐cervical region.2. In the rabbit, regeneration occurs 3 to 4 months after crushing, and between 1 year 2 months and 2 years 8 months after cutting.3. In the cat, regeneration of the autonomic efferent fibres was obtained 7 months after crushing, and in just over a year (374 days) when the nerve had been cut.4. Regeneration of cardiac vagus fibres was found to have occurred in a dog 10½ years after the right vago‐sympathetic had been cut high in the neck.5. In the same dog, periodic attacks of sickness and a fatal termination, probably due to a relative vagal paralysis, indicated that the cesophageal and gastric vagal fibres had not perfectly regenerated after ten years.6. In the majority of cases, both in cats and rabbits, stimulation below the neuroma gave a more marked inhibition of the heart and consequent fall in blood‐pressure than stimulation above.7. Independent results on heart as regards rate and force on stimulating the peripheral regenerating vagus were observed in a few animals.8. In one cat (No. 4) the peripheral regenerating vagus stimulated central to the neuroma gave a negative result, although stimulation peripherally to the neuroma produced marked inhibition. This apparent instance of peripheral regeneration is discussed in the text and a possible explanation offered.9. In one cat in which no functional regeneration of the central vagus or depressor was observed, but regeneration of at least certain branches of the cervical sympathetic, the thyroid on the operated side was atrophied as compared with the normal side.10. The eye and ear results of sympathetic paralysis disappeared in rabbits during the first few months; in cats during the third year; in one dog, eye and ear differences, lacrimation, and occasional salivation were still noticeable after ten years.11. Regeneration of the recurrent laryngeal fibres of the vagus (rabbits and cats), and functional recovery of the respiratory movements of the paralysed cord, were obtained and confirmed histologically.The expense of this research has been partly defrayed by grants from the Earl of Moray Fund and the Medical Research Council.