392 
T. F. WINCHESTER 
acute endo-arteritis. The histological changes in the seconc 
ary atheroma of horses are perfectly analogous to those o 
the spontaneous atheroma of man. Idiopathic atheroma, a 
seen in man, does not occur any more in the horse than in th 
other domestic animals. Atheroma in the horse is alwayi 
secondary. To be sure, one observes an idiopathic chroni 
endo-arteritis in many abdominal arteries of the horse, which 
however, never exhibits indications of atheromatous deger 
eration. 
11. In consequence of its position, the worm-aneurism oj 
horses is not open to physical examination, and, on tha 
account, cannot be diagnosed by physical signs; moreover, v 
offers no characteristic symptoms. Its termination by nip 
ture is extremely rare, the aneurisms of the abdominal aort; 
being more disposed to rupture than those of the anterio 
mesenteric artery. Of eighteen cases of known perforation 
fifteen opened into the peritoneal cavity, and thre* 
into the bowel. The dangerous symptoms of th' 
worm-aneurism are exclusively due to embolism an( 
thrombosis of the affected artery, arising from the parieta 
clot. The latter becomes especially dangerous through it 
increasing size and the softening which accompanies it. Th' 
absorption and shrinking of this parietal clot, be it organizer 
or not, is materially assisted by the high pressure to which it i 
exposed. 
12. The very marked symptoms of vascular obstruction- 
the sero-hemorrhagic intestinal infarct—in embolism am 
thrombosis of the mesenteric arteries, are easily explained b] 
paralysis of the muscular coat of the intestine, by the absencf 
of paucity of valves in the portal vein, by the readiness wit! 
which meteorismus (orflatus) arises, especially in herbivora 
and by the loose consistence of the intestinal walls of villi. 
13. The occlusion of the intestinal arteries, especially tha 
arising suddenly, always has for its result a partial or com 
plete paralysis of the portion of bowel which they supply 
The palsy of the intestine causes the forward movement 0 
the intestinal contents to cease, a stoppage of the faeces, < 
hindrance to the discharge of faeces and gas, and also that ex 
