CH. III.] THE NERVES OF MUSCULAR TUBES. 93 



influence of the mind, and the still more important influence 

 of the nerves. — (Compare § 207.) 



170. The nerves act principally in the other canals which 

 have a muscular structure, and numerous nerves, as the 

 oesophagus, intestinal canal, &c., by the stimulus of muscular 

 motion, so that these tubes are put in motion by the nerves for 

 the performance of those acts, of which their structure renders 

 them capable. When no natural obstacle is present in the 

 perves (47, &c.) to prevent the transit of the external impres- 

 Isions to the brain, and they are really sensitive (34), they may 

 be stimulated to action by the cerebral impression of external 

 sensations, and then the action is sentient (97, 129, 131), 

 although their actions are not usually sentient, but nervine 

 (162, 163). The oesophagus and intestines are often really sen- 

 sitive, and are then affected with spasms, as is proved by colic, 

 which has its seat in the intestines. Now, since in these cases, 

 the spasms are true sentient actions from external sensations 

 (from pain), these tubes do actually manifest some sentient 

 actions; although, in other cases, they are excited wholly by 

 other animal forces, and, although the will has no power over 

 them (162, 163). Nay, since the other sensational conceptions, 

 imaginations, foreseeings, &c., and the sensational desires and 

 aversions, can partly re-excite the material external sensations, 

 of which the sensitive nerves are susceptible at their origin 

 (66, &c., 93), so in like manner, they can excite movements in 

 these muscular tubes which are sentient actions ; as, for example, 

 when retching is excited by the anticipation of a nauseous taste, 

 and when the bowels are acted on by the imagination of a 

 purgative being taken. 



171. The membranes of the human body differ very much in 

 structure, — glandular, cellular, vascular, &c. ; the latter will be 

 treated of subsequently (208). The muscular membranes, as 

 the diaphragm and others which enclose different parts of the 

 body, particularly certain glands, are also sensitive, as we learn 

 from observation ; the diaphragm, in particular, has large nerves 

 which influence its movements by means of external im- 

 pressions, and the ligature of which causes the movements to 

 cease (Haller's ^ Physiology,^ § 403). Further, the motion of 

 the diaphragm is subject to the will, inasmuch as we can 

 change the respiration at pleasure. The remarks previously 



