340 MANUAL OF EQUINE MEDICINE. 



arteria ilia, ctecales, and colica inferior (arteria ilio-CEeco colica) arise, 

 less frequently the arteria colica superior at its origin, and the arteries 

 of the cfficum and colon in their course in the meso-osecum and meso- 

 colon The verminous aneurism also occurs in the coeliac artery 

 (Bauchschlagader), in the posterior mesenteric artery (gekros-arterie), 

 in the renal artery, and in the abdominal aorta. A horse is not unfre- 

 quently afflicted with several aneurisms of this kind at one and the same 

 time. Thus, in one case (described by Bollinger) there were six of these 

 aneurisms affecting the abdominal aorta and its branches in the same 

 horse The verminous aneurism may occur from the sixth month of life 

 onwards ; and with increasing age, the number of horses free from such 

 aneurisms becomes continually smaller. _ 



' The walls of the aneurism are, almost without exception, indurated. 

 In addition to the mesenteric connective-tissue, all the arterial coats, 

 and especially the tunica media, generally take part in this induration. 



' The changes in the intima present all stages of progressive and retro- 

 gressive m.etamorphosis, and are the least constant. _ 



' The changes vary from simple induration to idceration and calcih- 

 cation In addition to the palisade worms, one almost constantly finds a 

 parietal thrombus contained in the aneurism. It covers the inner walls, 

 either partially or completely, being in the latter case perforated by 

 arterial offshoots. This clot may occlude the artery, and it is not un- 

 frequently continued into the arterial branches (peripherally), or into 

 the aorta (centrally). Amongst the various changes that the clot under- 

 goes organization of its outermost layer and softening are the most 

 frequent. The constant occurrence of this clot is due to the presence of 

 the worms, to the inflammation, ulceration, and retrogressive affection 

 of the intima, and to the dilatation of the arterial tube.' 



3. STRONGYLUS TETRACANTHUS, or Four-Spined 

 Stroiigyle.— This nematode is found in large numbers 

 in the horse, ass, and mule, and though not an uncommon 

 cause of epizooty in this country, is not so frequently met 

 with on the Continent. 



These parasites infest the caecum and colon. Concerning 

 this parasite Cobbold writes : ' The males and females are 

 of about equal size, the largest females reaching nearly 

 three-quarters ".' 



In the sexually immature condition the worm occupies 

 the walls of the large intestine, where it gives rise to con- 

 gestion, ecchymosis, inflammation, and the formation of pus 



deposits. 



The species is readily recognised by its bright red colour. 



