DISEASES OF THE HEART, BLOOD VESSELS, AND LYMPHATICS. 83 



wound SO that the end will be exposed. In case the end of the bleed- 

 ing arteiy has retracted, a sharp-pointed hook, called a tenaculum, 

 is used to draw it out far enough to tie. The ligature should be 

 drawn tightly, so that the middle and internal coats will be cut 

 thi'ough. 



Another method of checking hemorrhage is called torsion. It con- 

 sists in catching the end of the bleeding vessel, drawing it out a little, 

 and then twisting it around a few times with the forceps, which lacer- 

 ates the internal coats so that a check is effected. This is very effec- 

 tual in small vessels, and is to be preferred to ligatures, because it 

 leaves no foreign body in the wound. A needle or pin may be stuck 

 through the edges of the wound and a string passed around between 

 the free ends and the skin (PI. XXVII, fig. 10), or it may be passed 

 around in the form of a figure S, as is often done in the operation of 

 bleeding from the jugular vein. 



ANEURISM. 



A circumscribed dilation of an artery, constituting a tumor which 

 pulsates synchronously with the beats of the heart, is called aneurism. 

 It is caused by disease and rupture of one or two of the arterial coats. 

 The true aneurism communicates with the interior of the artery and 

 contains coagulated blood. It is so deeply seated in cattle that treat- 

 ment is out of the question. Such abnormalities are ascribable to 

 severe exertion, to old age, to fatty or calcareous degeneration, or to 

 parasites in the blood vessels. Death is sudden when caused by the 

 rupture of an aneurism of a large artery, owing to internal hemor- 

 rhage. Sometimes spontaneous recovery occurs. As a rule no symp- 

 toms are caused in cattle by the presence of deep-seated aneurisms, 

 and their presence is not known until after death. 



A false aneurism results from blood escaping from a wounded 

 artery into the adjacent tissue, where it clots, and the wound, remain- 

 ing open in the artery, causes pulsation in the tumor. 



THROMBOSIS (OBSTRUCTION) OF THE ARTERIES. 



Arteries become obstructed as a result of wounds and other injuries 

 to them, as those caused by the formation of an abscess or the ex- 

 tension of inflammation from surrounding structures to the coats 

 of an artery. Arteries are also obstructed by the breaking off of 

 particles of a plug or clot, partly obstructing the aorta or other large 

 artery. These small pieces (emboli) are floated to an artery that is 

 too small to permit them to pass and are there securely held, pro- 

 ducing obstruction. These obstructions are shown Ijy loss of power 

 in the muscles supplied by the obstructed artery and by excitation 

 of the heart and by respiration after exercise. The loss of power may 

 not come into evidence until after exercise. 



