118 DISEASES OF THE STOMACH AND BOWELS 



intestines, reach the right heart and, after passing through 

 the lungs, the arterial circulation. According to some 

 authorities they wander direct from the intestines between 

 the leaves of the mesentery to the anterior mesenteric trunk. 

 They are found principally in this trunk or its principal 

 branch, the ileocecocolic artery. By irritating the inner 

 wall of the artery they produce a chronic endarteritis. The 

 results of the inflammation of the artery are: Thrombosis, 

 dilatation and calcification of the arterial wall (aneurysm). 



Notwithstanding that nearly all horses (about 90 per cent.) 

 suffer from this aneurysm, embolic colic occurs in only about 

 5 per cent. 



Pathogeneses. — ^The worm aneiirysm of the anterior 

 mesenteric artery produces disorder of the bowel in three 

 different ways: (a) Detached fragments (embolic) of the 

 thrombus may reach the peripheral intestinal arteries, (b) 

 The thrombus itself may become prolongated into branches 

 of the artery, (c) The thrombus may in rare instances 

 completely obstruct the lumen of the mesenteric trunk. 

 In all three of these cases, depending upon whether or 

 not the collateral circulation suffices, there residts anemia, 

 hemorrhagic infarction, and ultimately a necrosis of the 

 mucosa of the bowel. On necropsy, therefore, we find 

 principally the symptoms of a hemorrhagic inflammation 

 of the bowels with necrosis and at the same time occlusion 

 or thrombosis of the afferent and peripheral arterial branches. 



Symptoms. — ^The attack of colic usually begins suddenly, 

 mostly during work. In mild cases the attack resembles 

 somewhat spasmodic colic in that the pain is intermittent. 

 On rectal examination everything seems intact provided there 

 is no displacement secondary to the thrombosis; or we may 

 be able to feel fremitus over the region of the anterior mesen- 

 teric artery. In many instances the thrombus can be 

 palpated per rectum. In the severe type bloating is an 

 ordinary symptom. This form of colic tends to hang on 

 with periods of remission for one or two weeks although it 

 usually lasts but a few hours. It is frequently attended by 

 fever and sometimes the stools are blood-stained. It is very 

 apt to lead to enteritis, rupture of the stomach or bowel, 



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