DISEASES OF THE ARTERIES AND VEINS 471 



DISEASES OF THE ARTERIES AND VEINS 



Certain structural changes occur in both arteries and veins owing to 

 infiammator}- attacks and certain forms of degeneration and injuries 

 occasioned by the presence of parasites, &c. 



ARTERITIS 



Arteritis, or inflammation of the walls of an artery, is by no means a 

 rare disease in the horse. It is usually the result of some irritant acting 

 upon the vessel from within. 



In man the causative agent is commonly found to be some granulation 

 or vegetation occurring in the structure of the aortic valves. 



These, when sufficiently large, repeatedly strike the wall of the vessel 

 during the movement of the valves, and excite inflammation in the part 

 struck; or it may result from a portion of blood clot liberated from the 

 interior of a large vessel being carried away and arrested in a smaller one, 

 producing a plugging of the vessel, or embolism. 



In the horse the disease is most commonly seen in the anterior mes- 

 enteric artery and in that part of the aorta in immediate proximity to 

 it. It is the result of irritation excited in the vessel by the presence of 

 worms. The parasites Strongylus armatus frequently take up their abode 

 here, and by their presence induce inflammation in the vessel wall. 



The vessel, which is at first thickened, becomes soft and very much 

 like a piece of wet wash-leather. Its elasticity is impaired or altogether 

 lost, and in consequence it gradually yields to the pressure of the blood 

 stream, and ultimately becomes dilated and forms an aneurism. On the 

 internal surfoce there is frequently to be found a quantity of coagulated 

 fibrine, in which the parasites are embedded. 



Symptoms. — The chief symptoms of this disease are wasting, and 

 diarrhoea, and periodical subacute abdominal pain. The animal is dull and 

 listless, tucked up in the belly, feeds indiff'erently, and sometimes refuses 

 food altogether. If a sharp look-out be kept, small red worms will be 

 found in the excrement. 



In these cases the partial plugging of the mesenteric artery diminishes 

 the quantity of blood flowing towards the intestine. The function of that 

 organ is therefore imperfectly performed, resulting in periodical attacks 

 of diarrhoea, colic, and a general unthriftiness of the afi"ected animal. 



The patient sometimes brightens up and appears to have recovered, 

 when recrudescence of the disease occurs, and he goes back in condition, 

 and may succumb to the disease. 



