2 1 8 Veterina ry Medicine . 



horses Bollinger found 168 aneurisms, 153 in the anterior mesen- 

 teric, and its divisions, 4 in the coeliac axis and its divisions, 3 in 

 the hepatic artery, 3 in the posterior mesenteric artery, 3 in the- 

 renal arteries and 2 in the posterior aorta. 



The special predisposition of the anterior mesenteric artery is 

 variously accounted for : 1st. There is the obvious fact that its- 

 branches are distributed to the caecum and double colon, the 

 home of the mature parasite, and to the small intestines which 

 are first reached by the young parasites that are taken in with 

 the water and the food. These are therefore most likely to get 

 into the branches of this vessel and to follow them up toward its- 

 origin. 2nd. The anterior mesenteric artery distributes its 

 branches to the small intestines the most motile portion of the in- 

 testinal tract, and the caecum and colon the most heavily loaded 

 with solid ingesta, it is therefore the most subject to traction, 

 and distensions, and the more so that the parent trunk is ex- 

 tremely short and the divisions pass in all directions and to a 

 large extent at right angles, so that there is a dragging of the 

 walls apart as well as an obstruction to the blood flow and an in- 

 crease of internal tension. The distension, laceration, inflamma- 

 tion and softening of the internal coat have accordingly been re- 

 garded as the starting point of an endarteritis upon which the 

 parasites have been implanted as a further cause of trouble. 

 The teeth of the worm are absent in the larva in the artery. 



The irritation of the intima determines here as elsewhere 

 exudation, and coagulation, and the inflamed walls losing their 

 tone yield more and more readily to the internal tension. Some- 

 times the coagulum lines the aneurism or vessel all round, leav- 

 ing a narrow central passage through which the blood still flows ; 

 in other cases the clot extends into the adjacent smaller vessels, 

 completely blocking them and disturbing circulation and innerva- 

 tion in the parts which they supply. As a rule the parasites are 

 found in galleries hollowed out in the clot, and heads or tails may 

 be seen to project into the circulating blood. Sometimes they 

 are found imbedded in the arterial coat, or in an adjacent small 

 abscess. The formation of aneurisms in the other arterial trunks 

 may follow the same method. 



Embolisms. These come very naturally from the formation 

 of thrombi in the various arteries. The coagulum determined 



