Pathogenesis, 395 



and the formation of blood coagula, also after some time, a 

 thickening and a dilatation of the vessel wall. Sticker holds a 

 different view, namely, that the larvae become lodged in the vasa 

 vasornm, cause infarction in the media of the vessel, and then 

 mesoarteritis, or peri- and endarteritis. These changes are seen 

 most frequently in the anterior mesenteric artery, or in the art. 

 ileo-coecocolica, rarely simultaneously or exclusively in a branch 

 of this artery; also in the posterior mesenteric artery or in the 

 art. cceliaca. 



In 108 cases of aneurysms in horses Hering found the art. mesent. involved 100 

 times (92.6%), the arteria cceliaca five times (4.6%), the art. mesent. post, twice 

 (1.8%) and the art. renalis once (0.9%). Bollinger's sixty cases were distributed 

 as follows: Fifty-three times (83.3%), the art. mesent. thirty-two times in the 

 main trunk; ten times each in the upper and in the lower branch; once in a branch 

 of the small intestine ; twice (3.3%) in the abdominal aorta; twice (3.37( ) in the 

 art. cceliaca; once (1.6%) in the art. mesent. post.; and twice (3.3%) in the art. 

 renalis. In twenty-nine cases of aneurysma in the art. mesent. ant., Wall saw the 

 aneurysm in the main trunk of this artery only once (3.4%); in the other twenty- 

 eight cases (96.6%) it was found in the art. ileo-coecocolica. Adelmann found in 

 all of his ninety-five cases the aneurysm in the art. mesent. ant. ; in seventy-three 

 horses this artery and its branches alone were involved ; in one horse the art. mesent. 

 post, was affected simultaneously; in four horses the posterior aorta; in two horses 

 the art. cceliaca; in one horse the portal vein; in one horse the splenic artery and in 

 three horses the pulmonary arteries. In these eighty-five cases thrombosis was usu- 

 ally seen in the art. ileo-ccecocolica and also sixteen times simultaneously in the art. 

 col. ventralis ; ten times in the art. col. dors. ; seven times in the art. ileo-ccecalis, and 

 three times in an artery of the small intestine. 



The formation of a thrombus leads to a narrowing of the 

 lumen, provided that dilatation is not commensurate with the 

 diminution of caliber, or if the end of the thrombus projects 

 into the lumen of a branch. The diminution of the lumen rarely 

 goes on to complete obliteration in a main trunk, but complete 

 obstruction of lateral branches occurs somewhat more fre- 

 quently. 



Stenosis or complete obstruction of mesenteric arteries 

 may be brought about in a variety of manners. It may occur 

 that a thrombus formed somewhere increases gradually in size 

 until it closes the lumen completely. The more rapidly the 

 thrombus grows, the earlier may disturbances of circulation 

 come on after complete obstruction. There is also the possi- 

 bility that two or more neighboring and anastomosing arteries 

 are affected simultaneously by thrombosis ; in such a case even 

 a stenosis of not very high degree may become dangerous. One 

 cannot infrequently see that in non-obturating thrombosis of 

 the art. ileo-coecocolica or of the art. colica ventr., blood can get 

 in sufficient amount into the colon through the arter. colica dor- 

 salis, so that its blood circulation remains fairly normal. If, 

 however, the art. colica dors, becomes stenosed or completely 

 obstructed, local circulatory disturbances will come on with- 

 out fail. Cases are not rare in which a thrombus formed in a 

 main trunk will become elongated, and will reach and obstruct 

 the opening of an arterial branch. A thrombus formed in the 

 art. ileo-coecocolica and growing peripherally may reach or even 



