228 ANATOMY OF THE RABBIT 



of the ganglion. Delicate nerve strands connect the coeliac 

 and superior mesenteric ganglia, which are the largest of 

 those known as collateral (p. 74). 

 (/) The delicate nerves proceeding from the coeliac and 

 superior mesenteric ganglia accompany the corresponding 

 arteries to the respective organs which they supply, 

 forming the coeliac and superior mesenteric plexuses. 



Through these plexuses run postganglionic fibres (p. 75) from the 

 coeliac and superior mesenteric ganglia and from the ganglia of the 

 S3^mpathetic trunk, preganglionic fibres destined for the peripheral 

 ganglia, and visceral afferent fibres. In the pancreas it has been shown 

 that the gland-cells are innervated by parasympathetic fibres from 

 cell-bodies in ganglia within the gland and the blood-vessels are con- 

 trolled entirely by sympathetic fibres with their cell-bodies in the coeliac 

 and superior mesenteric ganglia. 



(g) The (greater) splanchnic nerve (n. splanchnicus major) of 

 the left side passes backward from its origin in the thorax 

 (see p. 336), around the reduced left crus of the diaphragm, 

 and, crossing the aorta obliquely, enters the coeliac and 

 superior mesenteric ganglia as well as sending branches to 

 the renal plexus. It is composed of preganglionic fibres 

 (p. 75). 



The ganglia just described transmit to the viscera nerve impulses 

 received from the spinal cord through the splanchnic nerves but also 

 probably transmit local reflex impulses received directly from the 

 viscera. 



Experimental section of the nerves in the living animal results in 

 vaso-dilation, stimulation in vaso-constriction. 



The lesser splanchnic nerve is absent as a distinct structure in the 

 rabbit. 



(h) The beginning of the inferior mesenteric artery and the in- 

 ferior mesenteric ganglion, with the related autonomic nerve 

 plexus, all of which are described on pages 241-2, may be 

 noted at this point. 



(i) An outlying portion of the pancreas (cf. p. 23G) is seen in 

 the peritoneum after the branches of the splenic artery 

 have been severed (4, a). This is the part already point- 

 ed out in the first paragraph of section 2. 



4. Trace the plan of branching of the coeliac artery, beginning 

 at the point of origin, and exposing the vessels in order. 



