112 DISEASES OF THE STOMACH AND BOWELS 



up by healthy horses (colts) with the bedding or grass of the 

 pasture and with the drinking water. From the bowel the 

 larvse pass "into the veins of the mucous membrane of the 

 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. 

 There are found principally in this trunk or its principal 

 branch, the ileocolic 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 aneurysm 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 results 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 fremitis 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 



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