44 SCIENCE PROGRESS. 



The inhibitory fibres of the vagus have also had their 

 origin and cell-connections investigated. Grossmann ^ ex- 

 amined the rootlets of the ninth, tenth and eleventh cranial 

 nerves to determine in which of these rootlets the inhibi- 

 tory fibres left the medulla. For purposes of reference he 

 divides the rootlets into the three groups as they are 

 anatomically arranged ; these groups he speaks of as group 

 {a), [b) and [c) respectively. The fibres of group [a] cor- 

 respond fairly well, though by no means entirely, with the 

 fibres forming the glosso-pharyngeal, group [b] with the 

 vagus, and group [c) with the medullary origin of the spinal 

 accessory. He examined each of these rootlets as they 

 leave the medulla, employing rabbits as the animals experi- 

 mented upon, for cardio-inhibitory nerves by unipolar 

 stimulation of each rootlet immediately as it arose from 

 the medulla, after cutting it through close to its origin or 

 after tearing it from the medulla. He found them in the 

 lower two or three rootlets of group (<5) and the upper 

 rootlet of group [a). F. Vas" has also examined these 

 same rootlets in the skull cavity for their effect upon the 

 heart. He tears through the rootlets and notes the effect 

 upon the heart and upon the blood pressure. He does not 

 find any cardiac nerves in the accessory rootlets. With 

 regard to the further connections of these fibres Gaskell ^ 

 showed that in the crocodile and alligator, by the degenera- 

 tion method, these fibres had no connection with cells in 

 the ganglion trunci, but were continued straight down as 

 medullated fibres to their termination in the heart substance, 

 where their endings were probably in relation with some 

 of the cardiac ganglion cells. This connection of the fibres 

 with intrinsic cardiac ganglia is shown by the action of 

 nicotine applied locally to the heart. '^ After the application 

 of nicotine the heart can no longer be inhibited by stimula- 

 tion of the vagus in the neck, though it can if the fibres in 

 the substance of the heart be stimulated. The vaous fibres 



o 



^ Pflilgers ArchiVy vol. lix., p. i, 1894. 



2 UngarArch.f. Med., iii., 1894. 



^Journ. of Physiol., vol. vii., p. 22 ^/ seq., 1885-6. 



^ See Langley and Dickinson, y^^/zr;/. of Phys., vol. xi., p. 279, 1890. 



