MOVEMENTS OF THE STOMACH. 409 



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

 the pyloric orifice, into the commencement of the Intestinal tube, is at first 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 ac- 

 tion," 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 intestines, the nutritious por- 

 tion of the ingested matter is gradually taken up by the bloodvessels and absorb- 

 ents ; and the residue, combined with excrementitious matters separated from 

 the blood, begins to assume the faecal character. A further absorption takes 

 place during the passage of the faecal matter through the large intestines; and thus, 

 by the time it reaches the rectum, it has acquired a considerable degree of con- 

 sistency. The ordinary Peristaltic movements of the Intestinal canal are fully 

 accounted for, by referring them to the contractility of the muscular portion of 

 its walls, called into action by direct stimulation ( 316) ; and that they are not 

 in any degree dependent upon nervous connection with the Cerebro-spinal centres, 

 is clearly shown by their continuance after the destruction of these. Some 

 Physiologists suppose that these movements are attributable to " reflex" action, 

 through a nervous circle furnished by the fibres and ganglia of the Sympathetic 

 system. This supposition, however, is entirely unnecessary ; since the Hallerian 

 doctrine of independent irritability, of the truth of which such cogent evidence 

 has been adduced ( 325 327), affords an adequate explanation of them. And 

 it will be found, on careful examination, to have no sufficient evidence in its favor; 

 the utmost which experiment can show, being that contractions *ftiay be excited 

 through the medium of the Sympathetic nerves. But the experiments of Valen- 

 tin, who, more than any other Physiologist, has succeeded in obtaining positive 

 results of this kind, also indicate that the motor influence does not originate in 

 the Sympathetic ganglia, but is derived from the Spinal cord. 3 The following 

 are his general results, so far as they apply to this part of the subject. The 

 lower part of the (Esophagus in the neck is made to contract peristaltically from 

 above downwards, by irritation of the roots of the first three cervical Spinal 

 nerves, and of the cervical portion of the Sympathetic, through which last the 

 former evidently operate. The thoracic portion of the oesophagus is made to 

 contract, by irritation of the lowest Sympathetic ganglion of the neck, and of 

 the higher thoracic ganglia, and also of the roots of the lower cervical Spinal 

 nerves. Muscular contractions of the Stomach are produced, by irritation of 

 the roots of the 4th, 5th, 6th, and 7th cervical nerves, and of the first thoracic 

 in the rabbit ; so that a distinct furrow is evident between the cardiac and pyloric 

 portion of the viscus; and the lower the nerve is irritated, the nearer to the pylo- 

 rus do the contractions extend. Irritation of the first thoracic ganglion of the 

 Sympathetic produces the same effect. Contractions of the Intestinal tube, 

 varying in place according to the part of the Spinal cord experimented on, may 

 be excited by irritation of the roots of the dorsal, lumbar, and sacral nerves, and 

 of the trigeminus ; and similar effects are produced by irritation of the lower part 

 of the thoracic portion, of the lumbar, and of the sacral portions of the Sympa- 

 thetic also of the splanchnic, and of the gastric plexus. 



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

 ductus choledochus is tied, constipation always occurs. The purgative action of Mercurials 

 seems to depend in great part upon the increase of the hepatic and other secretions which 

 it induces. 



2 "De Functionibus Nervorum Cerebralium et Nervi Sympathetici," book ii. chap. 2. 



