THE MUSCULAR MECHANISMS OF DIGESTION. 



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some way or other, by some direct action quite apart from the central nervous 

 system, is able to increase this power so that, without any aid from the central 

 nervous system, as after section of the vagi, adequate peristaltic move- 

 ments can, under favorable circumstances, be carried out. Nevertheless, in 



R.V 



Ret. 



Diagram to illustrate the Nerves of the Alimentary Canal in the Dog. 1 The figure is, for the 

 sake of simplicity, made as diagrammatic as possible, and does not represent the anatomical relations. 

 Oe. to Ret. The alimentary canal, oesophagus, stomach, small intestine, large intestine, rectum. 

 L. V. Left vagus nerve, ending on front of stomach, r.l. Recurrent laryngeal nerve supplying 

 upper part of oesophagus. R. V. Right vagus, joining left vagus in oesophageal plexus, oe. pi., sup- 

 plying posterior part of stomach and continued as R'. V. to join the solar plexus, here represented 

 by a single ganglion and connected with the inferior mesenteric ganglion (or plexus) m.gl. a. 

 Branches from the solar plexus to stomach and small intestine and from the mesenteric ganglion 

 to the large intestine. SpL maj. Large splanchnic nerve arising from the thoracic ganglia and 

 rami communicantes, r.c., belonging to dorsal nerves from the 6th to the 9th (or 10th). Spl.min. 

 Small splanchnic nerve similarly arising from 10th and llth dorsal nerves. These both join the 

 solar plexus and thence make their way to the alimentary canal, c.r. Nerves from the ganglia, 

 etc., belonging to llth and 12th dorsal and 1st and 2d lumbar nerves, proceeding to the inferior 

 mesenteric ganglia (or plexus), in. gl., and thence by the hypogastric nerve, n. hyp., and the hypo- 

 gastric plexus, pi. h;/p., to the circular muscles of the rectum, l.r. Nerves from the 2d and 3d 

 sacral nerves, S.2, S.3 (nervi erigentes), proceeding by the hypogastric plexus to the longitudinal 

 muscles of the rectum. 



the normal course of events, satisfactory movements are still further secured 

 by the reflex action through vagus fibres just described. Thus, in the dog, 

 the act of swallowing food or even the mere smell of food has been observed 

 to increase the movements of a piece of intestine isolated from the rest of 



1 It was not observed until too late that in the diagram of the nerves of the alimentary 

 canal in the dog, twelve dorsal nerves had been represented. The figure, as stated, makes 

 no pretence to anatomical exactness ; but it would have been better to represent either 

 thirteen or fifteen dorsal nerves. 



