Functional and histological changes in the vagus nerve of the cat after degenerative section at various levels

Circulatory Responses to Stimulation of Medullated and Non‐medullated Afferents in the Cardiac Nerve in the Cat

“…There is evidently also a fairly limited number of thinner, medullated fibres with diameters between 1.4 and 2.8 p m in the cardiac nerve. These fibres are probably equivalent to the presently described group I1 and constitute probably efferent vagal fibres to the heart (Daly and Evans 1953). The majority of the fibres in the cardiac nerve are presumably non-medullated, (Jarisch andZotterman 1948, Agostino et al 1957) corresponding to the fibre group I11 in the present study.…”

Activity of single efferent fibres in the cervical vagus nerve of the dog, with special reference to possible cardio‐inhibitory fibres

“…One Type I fibre had a higher conduction velocity inthe proximal vagus than in the distal vagus, which has been reported for some single fibres in the vagus nerve (Iggo, 1958;Paintal, 1962). This suggests that the fibres may become smaller as they descend, which might explain the difficulties in demonstrating histologically that there are myelinated efferent fibres in the vagal cardiac branches (Heinbecker, 1931;Heinbecker & O'Leary, 1933;Daly & Evans, 1953;Evans & Murray, 1954;Mizeres, 1955Mizeres, , 1957Agostoni, Chinnock, Daly & Murray, 1957). Type I fibres are probably not the same as those reported by Okada et al (1961b) since two Type I fibres were not affected by superior vena caval infusions; furthermore, there is a possibility that the fibres reported by these authors are not cardio-inhibitory (see Jewett, 1964).…”

Preserved vagal visceromotor function following destruction of the dorsal motor nucleus

“…Heinbecker & O'Leary (1933) first suggested that such might be the case since they found that after intracranial rhizotomy of the vagus, cardiac response to stimulation of the peripheral vagus was abolished, whereas duodenal and respiratory responses were preserved. Daly & Evans (1953) and Agostoni, Chinnock, Daly & Murray (1957) on the other hand stated that all vagal visceromotor responses were abolished by this procedure. The latter group noted, however, that in twenty-nine instances of vagal rhizotomy, bradycardia was obtained in one case and bronchial constriction in another; they could find no explanation for this unless incomplete rhizotomy might have been responsible in one experiment and concluded that all visceromotor vagal neurones have their somata in the medulla.…”