'400 Obstruction «{' tlic Mesentcrie Arteries. 



Avitli five anastoniosiiig arelies, occlusion of an artery of the 

 colon or cecum near its origin, provided that their anatomoses 

 or the peripheral portions of these arteries are not likewise 

 thrombosed. The more anastomoses are obstructed or at least 

 partially occluded at the same time, the smaller must be tlie 

 occluded territory if the collateral circulation may become es- 

 tablished at all. 



A very slowly progressing gradual narrowing of the lumen 

 of larger or of numerous smaller arteries does not necessarily 

 produce particularly grave disturbances, because the anasto- 

 moses and eventually the partly obstructed vessel have time to 

 gradually dilate. However, complete closure of the trunk of the 

 art. mesent. ant., of the art. ileo-coecocolica of the two arteries 

 of the colon, or of the arteries of the cecum near their places 

 of origin, also obstruction of several neighboring arteries of 

 the small intestines, will cause irreparable disturbances of cir- 

 culation, even if taking place gradually. 



Complete inhibition of the arterial blood supply to some portion of the intes- 

 tines will cause anemic necrosis. After an artery and its capillaries have become 

 sufficiently empty so that the pressure has been lowered to the pressure of the veins 

 of the affected region, the circulation of the blood ceases entirely and the capil- 

 laries contain much less blood than under normal conditions. Since obstruction of 

 all anastomoses of a mesenteric artery, which is a necessary condition for the occur- 

 rence of an anemic necrosis, very rarely takes place under natural conditions, anemic 

 necrosis in combination with hemorrhagic infarction will very rarely be seen; such 

 was, however, the ease in an observation by Caspar of obstruction in the region 

 of the art. mesent. post. If all larger anastomoses of this artery are obstructed 

 simultaneously or successively, very small anastomoses that remain open will admit 

 enough blood only to produce a hemorrhagic infarction in the two end pieces of the 

 affected intestine, while the median piece does not receive any blood at all. An equi- 

 librium of the blood supply can, of course, not lie established in this case. 



According to the claims based upon the experiments of 

 Virchow, Cohnheim, Panum, Litten, and in accordance with 

 the views generally adopted, thrombosis of the mesenteric arter- 

 ies leads to a fall of the blood pressure in the obstructed artery 

 to zero, whereupon in the severe cases, the blood from the veins 

 flows through the capillaries back into the artery. However, that 

 this is erroneous and that the course of events is as de- 

 scribed al)ove has been shown beyond doubt by the experiments 

 of Marek. 



Attacks of colic, which were fatal within twelve hours, occurred in a horse after 

 complete compression of the art. ileocoecolica; the wall of the cecum was flaccid and 

 very friable; in it as well as in the wall of the caudal section of the small intestines 

 there was hemorrhagic infarction. Ligation of one arteria colica alone caused an 

 attack of colic which lasted one and one-half to four hours but which ended in recov- 

 ery, while the simultaneous ligation of the art. colica dorsalis and ventr., near their 

 places of origin, caused a fatal attack of colic, necrosis of the colon and hemorrhagic 

 infarction of its mesentery. Ligation of the art. colica ventr., near its place of 

 origin, followed after several weeks by ligation of its anastomoses in the iliac flex- 

 ure, caused an attack of colic lasting one day, which, however, terminated in 

 recovery. 



The function of the intestine is only disturbed in thrombosis 

 of the mesenteric arteries when circulatory disturbances are 



