MOVEMENTS OF THE INTESTINES. 351 



external sphincter muscle with, striped fibres is placed 

 rather lower down, and more externally, and holds the 

 orifice close by a constant slight contraction under the 

 influence of the spinal cord. 



The peculiar condition of the sphincter, in relation to the 

 nervous system, will be again referred to. The remaining 

 portion of the intestinal canal is under the direct influence 

 of the sympathetic or ganglionic system, and, indirectly, or 

 more distantly, is subject to the influence of the brain and 

 spinal cord, which influence appears to be, in some degree, 

 transmitted through the vagus nerve. Experimental irri- 

 tation of the brain or cord produces no evident or constant 

 effect on the movements of the intestines during life ; yet 

 in consequence of certain conditions of the mind, the 

 movements are accelerated or retarded ; and in paraplegia 

 the intestines appear after a time much weakened in 

 their power, and costiveness, with a tympanitic condition, 

 ensues. Immediately after death, irritation of both the 

 sympathetic and pneumo-gastric nerves, if not too strong, 

 induces genuine peristaltic movements of the intestines. 

 Violent irritation stops the movements. These stimuli 

 act, no doubt, not directly on the muscular tissue of the 

 intestine, but on the rich gauglionic structure shown by 

 Meissner to exist in the sub-mucous tissue. This regulates 

 and controls the movements and gives to them their 

 peculiar slow, orderly, rhythmic, and peristaltic character, 

 both naturally, and when artificially excited. 



