238 



the veins may develop an atlieromntons condition wLen exposed to any 

 source of prolonged irritation. Atheroma may affect arteries in any 

 jiart of the body; in some instances almost every vessel is diseased, in 

 others only a few, or even parts of one vessel. It is a very common 

 result of endocarditis extending into the aorta, which we find perhaps 

 the most frequent seat of atheroma. As a result of this condition the 

 affected vessel becomes impaired in its contractile power, loses its nat- 

 ural strength, and in consequence of its inability to sustain its accus- 

 tomed internal pressure, undergoes, in many cases, dilatation at the seat 

 of disease, constituting awewmm. In an atheromatous vessel, calcare- 

 ous deposits soon occur, whicli render it rigid, brittle, and subject to 

 ulceration or rupture. In such vessels the contractility is destroyed, 

 the middle coat atrophied and beyond repair. Atheroma in the vessels 

 of the brain is a frequent cause of cerebral apoplexy. jS^o symptoms 

 are manifested by which we can recognize this condition during life. 



CONSTRICTION OF AN AKTERY. 



This is usually the result of arteritis, and may partly or wholly be 

 impervious to the flow of blood. When this occurs in a large vessel it 

 may be followed by gangrene of the parts; usually, however, collateral 

 circulation will be established to nourish the parts previously supplied 

 by the obliterated vessel. In a few instances constriction of the aorta 

 has i)roduced death. 



ANEURISM. 



Aneurism is usually described as true and false. True aneurism is a 

 dilatation of the coats of an artery over a larger or smaller part of its 

 course. Such dilatations are usually due to chronic endarteritis and 

 atheroma. False aneurism is formed after a puncture of au tirtery by 

 a dilatation of the adhesive lymph by which the puncture was united. 



Symptoms. — If the aneurism is seated along the neck or a limb, it ap- 

 pears as a tumor in the course of an artery, and pulsating with it. The 

 tumor is round, soft, and compressible, and yields a peculiar fluctuation 

 upon pressure. By applying the ear over it a peculiar purring or hiss- 

 ing sound may sometimes be heard. Pulsation, synchronous with the 

 action of the heart, is the diagnostic symptom. It is of a slow, expan- 

 sive, and heavy character, as if the whole tumor were enlarging under 

 the hand. Aneurisms seated internally may occupy the cavity of the 

 cranium, chest, or abdomen. As regards the first, little is known dur- 

 ing life, for all the symptoms which they produce may arise from other 

 causes. Aneurism of the anterior aorta may be situated very closely to 

 the heart or in the arch, and it is very seldom that we can distinguish it 

 from disease of the lieart. The tumor may encroach upon the wind-pipe 

 and produce difficulty in breathing, or it may produce pressure upon the 

 venae cavse or the thoracic duct, obstructing the flow of blood and lymph. 



