MOVEMENTS OF THE ALIMENTARY CANAL. 725 



venous plexuses in the walls and thus aid in driving the blood into 

 the portal system. Similar movements have been observed in 

 the human being. 



Cannon suggests a new and convenient nomenclature for the movements 

 of the stomach and intestines as follows: 



(1) Rhythmic segmentations. — The rhythmic localized contractions _de- 

 cribed in the preceding paragraph. Exhibited throughout the small intestine. 



(2) Diastalsis. — Downward moving wave of contraction with a preceding 

 wave of inhibition (myenteric reflex). Exliibited chiefly in the small intestine. 



(3) Anastalsis. — Upward moving wave of contraction without a pre- 

 ceding phase of inhibition Exliibited chiefly in the proximal colon. 



(4) Katastalsis. — Downward moving wave of contraction without a 

 preceding phase of inhibition. Exhibited chiefly in the stomach. 



Movements of the Intestinal Villi. — Hambleton * calls attention 

 to the fact that if the intestine of a Uving animal is opened and 

 spread out under suitable conditions so that the villi may be 

 examined under a binocular microscope, it can be shown that they 

 exhibit active movements of two kinds: First, lashing movements 

 from side to side in various directions; second, what might be 

 called pumping movements, in which the villi are alternately 

 extended and retracted. Doubtless these movements are due to 

 the contractions of the muscular slips, which run into the stroma of 

 the vilh from the muscularis mucosae. If we can suppose that 

 they occur during normal digestion, it is evident that they add a 

 mechanical factor which must help materially in the absorption 

 of the products of digestion. 



The Nervous Control of the Intestinal Movements. — There 

 is some evidence to show that the rhythmical contractions of the 

 intestines are muscular in origin (myogenic), while the more co- 

 ordinated peristaltic movements depend upon the intrinsic nervous 

 mechanism. The intestine is, however, not dependent for either 

 movement upon its connections with the central nervous system. 

 Like the stomach, it is an automatic organ whose activity is simply 

 regulated through its extrinsic nerves. 



The small intestine obtains its supply of extrinsic nerve-fibers 

 from two sources, a bulbar autonomic supply by way of the vagi 

 and a thoracic autonomic supply by way of the splanchnic nerves 

 and the superior mesenteric ganglia. Stimulation of the vagi causes 

 contraction or increased tonus in the intestinal musculature, while 

 stimulation of the splanchnics, on the contrary, causes relaxation or 

 inhibition of tonus, f The paths of these fibers through the central 

 nervous system are not known, but there are evidently connections 

 extending to the higher brain centers, since psychical states are 

 known to influence the movements of the intestines, and according 



* Hambleton, "American Journal of Physiology," 34, 446, 1914. 

 t For a discussion of the innervation of the small and large intestine, see 

 Gaskell, "The Involuntary Nervous System," 1916. 



