STRONGYLUS ARMATUS. 
391 
>sis, from simple induration to ulceration and calcification, 
the walls of the verminous aneurism one not unfrequently 
ils all the pathological changes exhibited by atheroma in 
n. Calcification is a common form of the retrogade pro- 
:5, and, in very rare cases, may pass on to the formation of 
13 bone. 
7. In addition to the palisade worms, one almost con- 
,itly finds a parietal thrombus contained in the aneurism, 
covers the inner wall either partially or completely, being 
he latter case perforated for arterial offshoots. The clot 
7 occlude the artery, and it is not unfrequently continued 
the arterial branches (peripherally) or into the aorta 
titrally). Amongst the various changes that the clot under- 
.3, organization of its outermost layer and softening are the 
■ t frequent. The constant occurrence of this clot is due to 
presence of the worms, to the inflammation, ulcerative 
1 regressive affection of the intima, and to the dilatation of 
arterial tube. 
!. The palisade worms are seldom absent from aneurisms 
le horse. Their not being present is merely an accidental 
rumstance. On the average, nine palisade worms go to a 
ainous aneurism, and eleven in the horse. The highest 
1 ber of worms found in one horse reached 121. Not in- 
:uently, also, palisade worms, or their coverings in the 
ti of larval skins, are found in the aneurismal walls. The 
1 igration and emigration of the palisade worms out of the 
btine into the aneurism, and the reverse, takes place, 
oably, as a rule, within the arterial circulation. The path 
ie worm does not appear to be always the same, inasmuch 
ley can also wander through the peritoneal cavity. The 
found in the aneurismal wails are probably mostly 
i strayed specimens. 
I. From a comparative pathological-anatomical point of 
') the developmental history of the aneurysma vermino- 
r proves that a circumscribed endo-arteritis can determine 
-ormation of an aneurism. 
d. Like the worm-aneurism itself, atheroma of the ab- 
unal arteries arises from a circumscribed acute and sub- 
