243 



CYANOSIS. 



This is a condition sometimes found in foals immediateh* after birth, 

 and is due to non-closure of the foramen ovale, which allows a mix- 

 tuer of the venous with the arterial blood in the left cavities of the 

 heart. It is characterized by a dark purple or bluish color of the visi- 

 ble mucous membranes, shortness of breath, and general feebleness. 

 Foals thus affected generally live only a few hours after birth. 



DISEASES OF ARTERIES — ARTERITIS AND ENDARTERITIS. 



Inflammation of arteries is rarely observed in the horse as a pri- 

 marj' affection. Direct injuries, such as blows, may produce a con- 

 tusion and subsequent inflammation of the wall of an artery; severe 

 muscular sfjrain may involve an arterial trunk; hypertrophy of the 

 heart, by increasing arterial tension, may result in the iH'oduciJon of 

 a general endarteritis. Septic infection maj' affect the inner coat and 

 ultimately involve all three, or it may be the result of an inflamma- 

 tion in the A'icinity of the vessels, etc. Inflammation of arteries, 

 wliate;,'er the cause may be, often leads to very serious results in the 

 development of secondary changes in their walls. Arteritis may be 

 acute, subacute, or chronic; wlien the inner coat alone is affected it 

 is known as endarteritis. 



Symptoms. — Arteritis is characterized by a painful swelling along 

 the inflamed vessel, throbbing pulse, coldness of the parts supplied 

 by the inflamed vessel, sometimes the formation of gangi-enous sloughs, 

 suppuration, abscess, etc. In an inflammation of the iliac arteries we 

 find coldness and excessive lameness or j)aralysis of one or both hind 

 limbs. 



Patlwlogy. — In acute arteritis we find swelling along the vessel, loss 

 of elasticity, friabilit}-, and thickening of the walls; a roughness and 

 loss of gloss of the inner coat, with the formation of coagula or pus in 

 the vessel. Subacute or chronic arteritis may affect only the outer 

 coat — periarteritis; both the outer and middle coat, or the inner coat 

 alone — endarteritis; and by weakening the respective coats leads to 

 rupture, aneurism, or to degenerations, such as bony, calcareous, 

 fatty, atheromatous, etc. It may also lead to sclerosis or increase of 

 fibrous tissue, especially in the kidneys, when it may result in the 

 condition known as arterio-capiJlary fibrosis. Chronic endarteritis is 

 fruitful in the production of thrombus and atheroma. Arteritis may 

 be limited to single trunks, or it may affect, more or less, all the 

 arteries of the body. Arteries which are at the seat of chronic endar- 

 teritis are liable to suffer degenerative changes, consisting chiefly of 

 fatty degeneration, calcification, or the breaking down of the degen- 

 erated tissue, and the formation of erosions or ulcer-like openings in 

 the inner coat. These erosions are frequently called atheromatous 

 ulcers, and fragments of tissue from these ulcers mav be carried into 



