134 



Disturbances of Circulation. 



3. Alterations of the lining of the vascular wall : Lesions of 

 the vascular intima resulting in the destruction of the endothelium 

 and thus causing a loss of the natural smoothness of its surface give 

 opportunity for adhesion of platelets and white blood corpuscles to 

 the roughened surfaces and give origin to thrombus formation 

 {adhesion thrombosis). In lacerations, incised and puncture 

 wounds as well as contusions of the vessels, thrombi invariably 

 form, an important feature in wounds both as regards healing and 

 preservation of life, the clot formation gradually closing the 

 rent in continuity of the vessel and checking the loss of blood. 

 Thrombosis also takes place in case of vascular changes caused bv 

 bacterial invasion, parasites, perforating neoplasms, and in vessels 

 in the neighborhood of active inflammatory lesions, as upon the 

 valves in case of endocarditis, in the vessels of the lungs in pneu- 



Fig. 5. 

 Thrombosis in a cavernous angioma of tiie liver of a cow. 



monia, in parasitism of the arteries by strongylits annatus, in case 

 of invasion of pyogenic bacteria in the umbilical vein, etc. 



As a rule two or three conditions favoring thrombus formation 

 cooperate to cause it ; thus when a thrombus is formed after 

 bacterial invasion of a vessel, it is partly the result of special 

 ferment production, partly due to injury of the intima. 



The composition of thrombi varies with the rapidity of forma- 

 tion and the causes of production. Those rapidly formed and 

 caused by special elaboration of ferment are often quite like the 

 clots of external haemorrhage, homogeneous and of a dark red color 

 throughout, being made up mainly of fibrin and red blood corpuscles 

 {homogeneous thrombi) ; microscopically the fibrin forms an intri- 

 cate reticulum of delicate threads in a radiating or stellate form 

 around ihe disintegrating leucocytes which furnish the fibrin fer- 

 ment (coagulation centers of Al. Schmidt and Ribbert). Stratified 



