582 DISEASES OF THE ARTERIES AND LYMPHATICS. 



enlarges by degrees, so that pulsation is in tliis case also a 

 marked feature in the tumour." — (Spence.) 



Many cases of aneurism in the horse are recorded, and most 

 commonly aneurisms of the anterior mesenteric artery and pos- 

 terior aorta have been met with. The accompanying drawino-, 

 which is taken from a specimen in the possession of Professor 

 Walley, will illustrate the common situation of aneurism. 



Fig. 111. — Aneurism of the posterior aorta, with calcareous 

 degeneration of the walls of the sac. 



a, Aorta, natural size. 



h. Small dilatation, with the cut ends of the anterior mesen- 

 teric and coeliac axis. 



c, Large aneurismal sac, laid open. 



There are records of scattered cases of aneurism in larc^e 

 numbers, but the most interesting memoir bearing on this sub- 

 ject appeared in the Vienna Quarterly of Veterinary Science 

 for 1852, by Dr. Bruckmllller. It refers to aneurism of the 

 anterior mesenteric artery. Hering was the first to indicate 

 the frequency of this lesion, but Gurlt doubted the correctness 

 of Bering's observations. Bruckmiiller examined carefully, 

 from the 22d May to the 30th September 1851, 65 horses, 

 with a view to determine the frequency of this aneurism, and 

 found only six animals perfectly free from it; 59, or 91 per 

 cent., had dilatation of the mesenteric artery to a greater or 

 less extent. In 19 cases there w^as simple thickening of the 

 arterial coats, without or with very slight dilatation ; 8 small 

 aneurisms from the size of a pea to a hazel nut ; 29 larger, 

 varying from the size of a walnut to that of a hen's Qgg ; and 

 3 with hardening of the coats. The ages of the animals varied 

 from six to twenty, chiefly from six to eleven. Aneurism is 

 therefore not a very rare, but a very common disease in the 

 horse ; and in a number of cases of mesenteric aneurism parasites 

 are found occupying recesses in the thickened coats. The 



