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DISEASES OF HEART, BLOOD VESSELS, AND LYMPHATICS. 265 
CONSTRICTION OF AN ARTERY. 
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, col- 
lateral circulation will be established to nourish the parts previously 
supplied by the obliterated vessel. In a few instances constriction of 
the aorta has produced death. 
ANEURISM. 
Aneurism is usually described as true or 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 an artery 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 
appears 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 hissing sound may sometimes be heard. Pulsation, syn- 
chronous with the action of the heart, is the diagnostic symptom. It 
is of a slow, expansive, 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 during life, for all the symptoms which they pro- 
duce 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 heart. The- 
tumor may encroach upon the windpipe and produce difficulty in 
breathing, or it may produce pressure upon the vena cava or the 
thoracic duct, obstructing the flow of blood and lymph. In fact, 
whatever parts the aneurism may reach or subject to its pressure, may 
have their functions suspended or disturbed. When the tumor in the 
chest is large, we generally find much irregularity in the action of the 
heart; the superficial veins of the neck are distended, and there is 
usually dropsical swelling under the breast and of the limbs. There 
may be a very troublesome cough without any evidence of lung affec- 
tion. Sometimes pulsation of the tumor may be felt at the lower 
part of the neck where it joins the chest. When the aneurism occurs 
in the posterior aorta no diagnostic symptoms are appreciable; when 
it occurs in the internal iliac arteries an examination per rectum will 
reveal it. 
There is one form of aneurism which is not infrequently over- 
looked, affecting the anterior mesenteric artery, primarily induced by 
a worm—Strongylus vulgaris. This worm produces an arteritis, with 
