MOVEMENTS OF THE STOMACH. 137 



sensations, conjoined with the emotional state which they originally excited, 

 may itself become an efficient cause of the action, at least in individuals of 

 peculiarly irritable stomachs or of highly sensitive nervous systems ; for this 

 plays downwards upon the seusorial centres, in such a manner as to excite 

 in them the same condition as that which was originally produced through 

 the medium of the sensory nerve when the object was actually present. (See 

 chap, xiii, sec. 3.) 



94. The passage of the Chyme, or product of the gastric digestion, through 

 the pyloric orifice, into the commencement of the Intestinal tube, is at h'rst 

 slow ; but when the digestive process is nearly completed, it is transmitted 

 in much larger quantities. The pyloric orifice, like the cardiac, is furnished 

 with a sphincter muscle ; but how far its contractions are dependent upon 

 " reflex action," has not yet been ascertained. The ingested matter, which 

 undergoes further changes of a very important character within this portion 

 of the canal, is gradually propelled onwards by the peristaltic contractions 

 of its walls; and these are excited by the contact, either of the products of 

 digestion or of the secretions poured in by the various glands that discharge 

 their products into the intestinal tube. 1 In its progress along the small in- 

 testines, the nutritious portion of the ingested matter is gradually taken up 

 by the bloodvessels and absorbents ; and the residue, combined with excre- 

 mentitious matters separated from the blood, begins to assume the fecal 

 character. A further absorption takes place during the passage of the fecal 

 matter through the large intestines; and thus by the time it reaches the 

 rectum it has acquired a considerable degree of consistency. 



95. The nervous supply of the intestines is derived essentially from the 

 sympathetic, system ; though a few fibres may be derived from the pneumo- 

 gastrics. The sympathetic fibres proceeding from the coeliac, mesenteric, 

 and other plexuses accompany the bloodvessels to the intestines, and form a 

 chain of nerves and nervous ganglia, the Plexus myentericus, one portion of 

 which has been shown by Auerbach, to lie between, and to supply both the 

 circular and longitudinal layers of muscular tissue of the small intestines, 

 and to be situated on the outside of the longitudinal layer in the large in- 

 testine, whilst another portion, discovered by Meissner, lies in the submu- 

 cous areolar tissue, and is probably destined for the supply of the muscularis 

 mucosu!, or muscular layer of the mucous membrane. 2 It might at first 

 sight appear to be easy to determine the precise influence of the nervous 

 system upon the muscular walls of the intestines, but experience has shown 

 that the investigation is amongst the most difficult in experimental physi- 

 ology, various results having been obtained according to the animal experi- 

 mented on ; the nature of the stimulus applied ; the precise part stimulated ; 



1 The Bile seems to Lave an important share in producing this effect ; since, when 

 the ductns choledoeluis is tied, constipation always occurs. M. Legros and Onimus 

 (liobin's Journal de 1'Anat., 1869, pp. 37 and 163) have shown by tracings taken 

 from a caoutchouc ball introduced into the intestines, that the peristaltic contrac- 

 tions move more rapidly in the duodenum (sometimes traversing eight inches in the 

 minute) than in the caecum (six inches) of the dog. 



2 Auerbach, Canstatt's Jahresbericht, 1862, p. 174; Manz, Die Nerven und Gnn- 

 glien des Saugethierdarms, 1859; Krause, Studien des Phys. Instit. zu Breslau, 1863, 

 p. 41 Unters. ub. einig. TJrsach. der peristalt. Beweg. des Darin-canals ; and Vir- 

 chow's Archiv, 1864, p. 457. According to Gerlach (abstract in Humphry and Tur- 

 ner's Journ. of Anat., vol. viii, 1874, p. 173) the myenteric plexus of Auerbach con-' 

 tains highly vascular ganglia and fasciculi of fibres, formi.ng primary and secondary 

 networks. From the secondary plexuses tine fibres arise, each of which ends in a 

 corpuscle that may give off one or two processes, ending between the muscular fibres. 

 Klein (Quart. Journ. of Mic. Sci., Oct. 1873) describes, in addition to the above, 

 isolated ganglion-cells, between the circular and longitudinal muscular coats. 



10 



