398 Obstruction of the Mesenteric Arteries. 



it* an anastoniosiiig arcli, situated in tlio mesentery of the small 

 intestines or of tlie small colon (Fig. 40 j, o), or a branch aris- 

 ing from these arches or from the arteries of the colon or cecum, 

 has been closed up. The obstruction of an artery of the small 

 intestines (s), which has only two anastomosing arches, or the 

 obstruction in one place of one of the arteries of the colon or 

 cecum, near its peripheral portion, are likewise without danger. 

 In all of these examples it is, however, necessary that the re- 

 spective anastomosis has remained open. In the cases as given 

 above the rich anastomoses permit enough arterial blood from 

 neighboring arteries to get into the excluded territory, so that 

 a decrease of blood pressure does not occur. 



In contradistinction to the above, there will be developed 

 either a temporary or a permanent disturbance of blood circu- 

 lation of the intestines if one or more arteries of the small in- 

 testines are occluded, from which there branch at least three 

 anastomosing arches with neighboring arteries, or with arteries 

 supplying the small colon. This may also occur in occlusion 

 of at least one artery of the colon or cecum near its place of 

 origin, or of two points not very near to each other (in super- 

 imposed arrangement of the emboli). If the art. ileo-ccecoco- 

 lica or the art. mesent. ant. are themselves occluded or much 

 narrowed in their lumen, circulatory disturbances are never 

 absent; the same is also the case if, together with the above 

 mentioned arterial branches, its anastomosing branch is also 

 obstructed. Obstruction of the peripheral arterial branches 

 may sometimes become dangerous when a stenosis in the cen- 

 tral portion of the neighboring artery is present simultaneously ; 

 the narrowing of the lumen may be unimportant in itself but 

 it may cause a diminution of the blood supply in combination 

 with embolism in the peripheral branch. In all of these cases 

 of anastomoses too narrow for the region which has been 

 totally excluded from the arterial blood supply, or in which the 

 narrowing in a main trunk has greatly diminished the floAV of 

 blood, the blood pressure becomes lowered, although without 

 ever sinking down to zero. 



Lowering of the arterial blood pressure in the excluded 

 territory causes a decreased velocity of the capillary current, 

 because the difference between arterial and venous pressure, 

 which propels the blood through the capillaries, is diminished. 

 The decrease of the caliber of arteries and capillaries leads to 

 a more or less intense arterial anemia and, in consequence of 

 the retardation of circulation, to an accumulation of carbon- 

 dioxide in the l)lood and the tissues of the affected territory. 

 The retardation of circulation within a short time produces such 

 nutritive disturbance of the capillary walls that they lose their 

 tonicity and permit the constituents of the blood to extravasate. 

 The loss of tonicity may, however, also be due in part to irri- 

 tation by the intestinal contents. Capillaries of the intestinal 

 mucosa which have lost their tonicitv, will ])ecome strongly 



