DEGLUTITION AND DEFECATION. 151 



the stomach to the rectum, may take place without any connection with the 

 nervous system, being due to the direct stimulation of the contact of food, there 

 is now ample evidence ; and though some may still be found who deny the 

 Hallerian doctrine, that muscular fibre possesses in itself the property of con- 

 tractility, so much additional evidence of its truth has been recently adduced, 

 whilst the fact itself is so conformable to the analogy supplied by others, that 

 it will be here unhesitatingly adopted (See Chapter V.). Mr. Grainger and 

 some other physiologists have supposed that the peristaltic movements of the 

 alimentary canal are due to a sort of reflex action, taking place through the 

 ganglia of the Sympathetic system of nerves, especially, of course, the semiJunar. 

 This supposition, however, has little or no evidence to support it; for it has 

 been fully proved that the muscular contractions will continue long after the 

 tube has been separated from its nervous connections through its whole extent ; 

 and the only evidence in its favour is derived from the contractions which 

 may sometimes be induced in parts of the tube which are at rest when the 

 sympathetic nerves supplying them are irritated. Some very interesting 

 experiments have been recently published by Valentin, by which the fact that 

 such contractions may be induced (which has been denied by some) is clearly 

 substantiated ; but it is also shown that the motor influence does not originate 

 in the Sympathetic ganglia, but in the Spinal Cord. The following are the 

 general results of upwards of three hundred experiments, so far as they apply 

 to this subject. The pharynx may not only be excited to contraction by irri- 

 tation of the pharyngeal branches of the Par Vagum, or of the roots of the 

 Spinal Accessory, from which their motor power is derived (as will be hereafter 

 explained), but also by stimulating the roots of the first two Cervical nerves; 

 and the lower part of the cesophagus in the neck is made to contract peristalti- 

 cally from above downwards, by irritation of the roots of the first three Cervical 

 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 irrita- 

 tion 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 irritated, the 

 nearer the pylorus 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 Sympathetic, also of the splanchnic, and of the gastric 

 plexus. 



201. From these facts it is evident, that the movements of the Intestinal 

 tube may be influenced by the Spinal Cord; and that what is commonly termed 

 the Sympathetic nerve, is the channel of that influence, by the fibres which it 

 derives from the Spinal system. But it by no means thence follows, that the 

 ordinary peristaltic actions of the muscles in question are dependent on a 

 stimulus reflected through the spinal cord, rather than on one directly applied 

 to themselves. It is clear that, although these movements are of the first im- 

 portance to the welfare of the system, such means of sustaining them are feeble, 

 compared to those which we find provided for the maintenance of the distinctly 

 reflex actions of deglutition, respiration, &c. The difficulty with which any 

 evidence can be obtained of the connection, is a sufficient proof of this. On 

 the other hand, we do know that these peristaltic movements are influenced 



