245 



its course. Such dilatations arc 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. 



Sijinptouis. — 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 pecul- 

 iar 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 symjDtom. It 

 is of a slow, expansive, and heavy character, as if the whole tumor 

 were enlarging under the hand. Aneurisms seated internally may 

 occupj'- 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 maj^ encroach upon the wind-pipe and produce difficulty in 

 breathing, or it may produce pressure upon the vente cavfe 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 trouljjlesome 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. AVlien the aneurism occurs in 

 the posterior aorta no diagnostic sj^mptoms 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 unfrequently overlooked 

 affecting the anterior mesenteric artery, primarily induced by a worm — 

 the Strongylus armatus. This worm produces an arteritis with athe- 

 roma, degeneration, and dilatation of the mesenteric arteries, associ- 

 ated with thrombus and aneurism. The aneurism gives rise to colic, 

 which appears periodically in a verj^ violent and often i)ersistent type. 

 Ordinary colic remedies have no effect, and after a time the animal 

 succumbs to the disease. In all cases of animals which are habitually 

 subject to colicky attacks i^arasitic aneurism of the anterior mesen- 

 teric artery may be suspected. 



Pathology. — Aneurisms may be diffuse or sacculated. The diffuse 

 consists in a uniform dilatation of all the coats of an arter}', so that it 

 assumes the shaj)e of a cylindrical swelling. The Avail of the aneurism 

 is atheromatous or calcified ; the middle coat may be atrophied. The 

 sacculated or circumscribed aneurism consists either in a dilatation of 



