50 SCIENCE PROGRESS. 



causes contraction of the crop, gizzard and proventriculus, and 

 if while these parts are thus firmly contracted the vagus be 

 stimulated, a dilatation of the gizzard and proventriculus is 

 produced. In these two ways then the presence of in- 

 hibitory fibres in the vagus is demonstrated. 



With regard to the presence of nerve cells upon the 

 course of these fibres, Gaskell ^ showed in his experiments 

 upon alligators and crocodiles that the fibres for the stomach 

 contained in the vao-us were connected with nerve cells in 

 the ganglion trunci vagi, and that here too they became 

 non-medullated. 



Langley and Dickinson "' have further shown that the 

 inhibitory fibres contained in the splanchnic terminate in 

 cells in the coeliac ganglion, and that the motor fibres of the 

 vagrus do not become connected with cells in the solar 

 plexus or its immediate offshoots. After painting the 

 coeliac plexus with nicotine the rhythmic movements of the 

 stomach are greatly increased, and stimulation of the 

 splanchnic no longer interferes with that rhythm. Steinach '^ 

 describes motor fibres for the stomach of the frog in the 

 vagus, and also in the posterior roots of the third and fourth 

 spinal nerves. 



Small Intestine. — It has been commonly stated that 

 the arrangement of the double nerve-supply of the small in- 

 testine is that the one set, vagus fibres, cause contraction 

 of the circular and inhibition of the longitudinal fibres, the 

 second set, splanchnic fibres, cause contraction of the 

 longitudinal and inhibition of the circular fibres. The view 

 that the general function of the vagus is excito-motor and 

 of the splanchnic inhibitory appears however to be the one 

 which results from the experiments of most later observers, 

 though at times the splanchnic may give rise to contrac- 

 tions but not of the ordinary peristaltic character. These 

 irregular contractions caused by stimulation of the splanch- 

 nic may well be due to secondary effects brought about 

 by the constricting influence which the nerve exerts over the 

 blood-vessels. 



Houckgeest ^ in his experiments upon peristalsis con- 



^ Loc. cit. - Loc. cit. ^ Loc. cit. ^ Loc. cit. 



