WORK UPON VISCERAL AND ALLIED NERVES. 45 



therefore from their medullary origin to their termination 

 in the intrinsic ganglia form the prae-ganglionic fibres, from 

 the ganglion cells to the heart muscle terminals the post- 

 ganglionic. This double segmentation is also confirmed 

 by a degeneration method by Nikolajew/ 



INNERVATION OF THE MUSCULAR WALLS OF THE ALI- 

 MENTARY CANAL. 



CEsophagus. — It has long been known that peri- 

 staltic contractions of the esophagus may be produced 

 by stimulation of the vagus either in the neck or thorax, 

 Gaskell ^ investigated the function and course of these 

 fibres, choosing crocodiles and alligators for his ex- 

 periments, because in these animals the two vagal ganglia, 

 ganglion jugulare and ganglion trunci, are separated by the 

 whole of the cervical portion of the vagus. Stimulation of 

 the nerve in the crocodile either above or below^ the gang- 

 lion trunci produced a strong peristaltic contraction of the 

 oesophagus extending through both the cervical and thoracic 

 portions and ending in a contraction of the stomach. In 

 the alligator the course of the fibres is a little different, those 

 for the thoracic portion running as in the crocodile, whilst 

 the fibres for the cervical portion " pass directly to it pro- 

 bably by way of the large conjoint vagus and glossopharyn- 

 geal ganglion and the pharyngo-laryngeal nerve. 



The presence of nerve cells on the course of these fibres 

 was next investigated by removal of a piece of the vagus in 

 the neck and observation of the effects of stimulation of the 

 nerve above and below the ganglion trunci. It was thus 

 proved that the motor fibres for the thoracic portion of the 

 oesophagus have nerve cells interposed upon their course, 

 and that these cells are situated in the ganglion trunci. In 

 the crocodile the fibres for the cervical portion of the oeso- 

 phagus pass through the ganglion without coming into 

 connection with the nerve cells. These fibres above the 

 ganglion are fine medullated fibres, whereas below the 

 ganglion they are found to be non-medullated. 



1 Arch.f. {Anat u.) Physiol., suppl., p. 67, 1893. 

 ^ Journ. of Physiol., vol. vii., p. 19, 1886. 



