288 NERVOUS INFLUENCES AFFECTING INTESTINAL MOVEMENTS. 



This state of rest of the intestine is thus widely different from that attending 

 the condition of aperistalsis. Persistent stasis of blood in the intestinal vessels 

 leads finally to intestinal exhaustion, as, for instance, when thrombosis occurs in 

 the intestinal vessels after transfusion of blood from a different species. Distention 

 of the vessels with indifferent fluids, after compression of the aorta had previously 

 excited active peristalsis, likewise causes cessation of peristaltic movement. In 

 the same category belongs also the condition of rest noted after the temperature 

 of the intestine has been reduced to 19 C. Severe intestinal inflammation also 

 has a similar effect. Under favorable conditions the intestine may recover from 

 this stage of exhaustion after the irritation has ceased. This takes place, as a 

 rule, through a transitional stage attended with active peristalsis. Thus the intro- 

 duction of arterial blood into the vessels of the exhausted intestine causes at first 

 active peristaltic movements, followed by normal peristalsis. 



The continuous application of strong stimuli finally causes complete 

 paralysis of the intestine in human beings as seen after inflammations, 

 traumatisms, incarcerations, and the like. The intestine becomes 

 greatly distended, as the paralyzed muscularis is no longer able to offer 

 any resistance to the gases expanded by the heat (meteorism). 



The Peripheral Intestinal Nerves. Of the nerves passing to the intestine the 

 pneumogastric nerve increases the movements of the small intestine and the upper 

 portion of the large intestine, either by conveying the stimuli applied to it to 

 the myenteric plexus, or by causing contractions of the stomach, which, in turn, 

 as true mechanical impulses, excite the intestine to movement. The pneumogastric 

 nerves also contain several inhibitomotor fibers. 



The splanchnic nerve -the greater derived from the sixth to the ninth, and 

 the lesser from the tenth and eleventh dorsal ganglia is (i) the inhibitory nerve 

 for the intestinal movements, but only so long as the blood in the capillaries has not 

 become venous while the circulation in the intestine remains undisturbed. If the 

 latter condition has arisen, irritation of the splanchnic causes increased peristalsis. 

 If arterial blood be introduced, the inhibitory action is prolonged. Irritation of 

 the origin of the splanchnic nerve in the dorsal cord also produces the inhibitory 

 effect under analogous circumstances, even in the presence of irritation of the 

 spinal cord as a result of strychnin-poisoning, with the occurrence of general 

 tetanic convulsions. O. Nasse believes that it may be concluded from the experi- 

 ments that, in addition to these readily exhausted inhibitory fibers, paralyzed by 

 venosity of the blood, there are present (2) motor fibers that are excitable for 

 a longer time, inasmuch as stimulation of the splanchnic nerve after death always 

 causes peristalsis of the stomach and intestines, as does stimulation of the pneu- 

 mogastric nerve. (3) The splanchnic nerve is also the vasomotor nerve of all of 

 the arteries and veins of the intestines, including the portal vein, thus controlling 

 the largest vascular area of the body. Stimulation of the splanchnic nerve causes 

 contraction, its division dilatation, of all of the intestinal blood-vessels possessing 

 muscle-fibers. In the latter event an enormous accumulation of blood takes place 

 in the intestinal vessels, so that anemia of other parts of the body results, and 

 in consequence even death may take place from anemia of the medulla oblon- 

 gata. (4) The splanchnic nerve is, finally, the sensory nerve of the intestines, 

 and, as such, it is extremely sensitive. 



Almost all the cells of the solar plexus are included in the course of the fibers 

 of the splanchnic nerve. Nicotin paralyzes these cells, while the peripheral fiber 

 retains its irritability. 



Stimulation of the nervi erigentes causes contraction of the longitudinal mus- 

 cular fibers and relaxation of the circular fibers of the rectum; while irritation of 

 the hypogastric nerves has the opposite effect according to Fellner. 



Stimulation of the sigmoid gyrus on the cerebral cortex of the dog, as well 

 as of parts lateral to and behind it, excites intestinal movements through the 

 pneumogastric nerves, as does likewise stimulation of the optic thalamus. Inhibi- 

 tory fibers pass from both of these situations through the spinal cord, from which 

 they make their exit near the middle of the dorsal cord. 



The drugs that affect the intestine are (i) those that diminish the irritability 

 of the myenteric plexus, and thus decrease peristalsis, even to the point of intes- 

 tinal rest, like belladonna; (2) those that stimulate the nerves inhibiting peris- 

 talsis, and paralyze in large doses, like opium or morphin. The drugs of these 

 two classes cause constipation. Elevation of temperature (also during fever) 



