2 14 Veterinary Medicine. 



found 1 68 aneurisms, 153 in the anterior mesenteric, and its 

 divisions, 4 in the cceliac 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 : ist. 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 inge.sta, 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 para- 

 sites have been implanted as a further cause of trouble. We 

 must not forget, however, that the sharp circle of teeth of the 

 parasite, by which it fixes it.self on the intima of the vessel are 

 quite enough to produce initial endarteritis, without any assist- 

 ance from distension, traction or laceration. 



The irritation of the intima from whatever cause determines 

 here as elsewhere exudation, and coagulation, and the inflamed 

 walls losing their tone yield more and more readily to the in- 

 ternal tension. Sometimes the coagulum lines the aneurism or 

 vessel all round, leaving a narrow central passage through which 

 the blood still flows ; in other cases the clot extends into the ad- 

 jacent smaller vessels, completely blocking them and disturbing 

 circulation and innervation 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 tnniks mav follow the same method. 



