5 2 THE IN VOL UNTAR Y NER VO US S YSTEM 



which arise motor nerves to that part of the involuntary intes- 

 tinal musculature, which is associated with the vagus portion of 

 the cranial outflow of connector nerves ; just as some of the 

 motor cells in the mesenteric ganglia give origin to motor fibres 

 to that part of the involuntary intestinal musculature, which is 

 associated with the thoracico-lumbar outflow, namely, the sphincter 

 system (Fig. 5). 



In the region of the oesophagus such motor cells are still 

 found, but no longer in the same position as in the intestine : 

 they have come more to the surface so that they form a super- 

 ficial plexus lying on the unstriped muscle of the oesophagus. 



A diverticulum of the intestine forms the lungs, and this 

 diverticulum carries with it the same innervation as the intes- 

 tine from which it was derived ; its voluntary musculature, as 

 in the pharynx and oesophagus, receives motor fibres direct from 

 the motor cells of the nucleus ambiguus in the medulla oblongata ; 

 its involuntary musculature, the unstriped muscles surrounding 

 the bronchi, receives motor fibres from motor cells in the lungs 

 themselves, and the vagus nerve supplies connector fibres to 

 these nerve cells (Fig. 3, B and C). 



Another diverticulum of the intestine forms the liver, the gall 

 bladder of which is surrounded by unstriped muscles. The 

 motor cells which supply motor fibres to this musculature are, 

 according to Bainbridge and Dale, situated in the organ itself 

 and their connector fibres belong to the vagus nerve. 



The part of the intestine associated with the vagus nerve finds 

 its lower limit at the end of the small intestine. The vagus never 

 sends fibres into any part of the large intestine. The large in- 

 testine is however part and parcel of the tube of the alimentary 

 canal, and one would naturally expect it to be innervated in the 

 same manner as the small intestine, although its motor cells are 

 connected with the central nervous system by connector fibres 

 in the pelvic nerve arising from the sacral end of the body, while 

 those of the small intestine are connected with the central nervous 

 system by connector fibres in the vagus nerve arising from the 

 cranial end of the body. 



I will now consider the sacral outflow and determine what is 

 the great characteristic of the motor nerve cells belonging to this 

 group. Their connector fibres pass, as already mentioned, from 

 the spinal cord in the anterior roots of the 2nd and 3rd sacral 



