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 gangi-ene 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 ma}' 

 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 difliculty 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 pails 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 mufh ii-regularity 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 witliout 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. AMien 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 — StrongyJus vulgaris. This worm produces an arteritis, with 



