THROMBOSIS AND EMBOI^ISM. 



Definition. Thrombosis — clotting in the vessel. Embolism, plugging of 

 the vessel. Thrombus may form in any bloodvessel. Embolism occurs in 

 arteries. Clot follows the blood current. Causes of clotting — fibrinogen, 

 paraglobulin, fibrine ferment ; foreign bodies ; parasites ; air ; blood that has 

 been exposed, (transfusion ; aerial germs ; disea.se germs ; chemical coagu- 

 lants ; high and low temperatures ; breaches of endothelium , congestion or 

 inflammation of the serosa ; stasis of blood and extension of clot ; ligature 

 near a branch vessel : deoxidation and carbonization of blood, marasmus ; 

 neoplasms ; traumas of the vascular coats ; infarction. Causes of blocking ; 

 disintegration of clots, softening, liquefaction, ulceration, action of microbes ; 

 excess of white globules ; air ; fat ; parasites. Pathogenesis ; complete oc- 

 clusion of vessel ; infarction ; sequestrum ; collateral circulation ; embolism 

 of external iliac or femoral artery ; effects on pulse ; during rest ; atrophy ; 

 lameness comes on with exertion ; disappears under rest ; circulation inade- 

 quate to sustain active function. Embolism of internal iliac artery ; effect 

 on pulse ; on tail and pelvic organs. Embolism of axillary artery ; effect 

 on pulse, action, nutrition. Embolism of mesenteric artery ; verminous ; 

 effects on innervation and circulation ; spasms, congestions, paresis ; invo- 

 lution. Treatment : expectant ; alkalies ; gentle exercise, time. 



Definition. Thrombosis is the blocking of a blood vessel by 

 a clot formed in its interior by the deposition of layer above layer 

 on its inner coat. 



Embolism is the blocking of a bloodvessel by a clot or other 

 solid body formed at a distant point of the circulation floated on 

 in the blood stream, and arrested when it reaches a vessel too 

 small to transmit it. 



A thrombus may be formed at any point of the circulatory ap- 

 paratus (heart, arteries, veins) whenever the conditions are such 

 as to determine coagulation of the blood. An embolism, on the 

 contrary, is a disease of the arteries, since in these the blood cur- 

 rent, proceeding centrifugally from the greater to the lesser, inev- 

 itably carries the moving solid to a point too narrow to allow of its 

 further progress. Thus clots originating in the systemic veins 

 or right heart pass to the lungs and produce embolism of the pul- 

 monary arteries whereas tliose formed in the pulmonary vein or 

 left heart are arrested in some part of the systemic arteries. Clots 

 formed in the portal vein, however, are arrested in the hepatic ves- 

 sels into which that trunk breaks up. 



Causes of Thrombus. The production of a thrombus may be 



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