2 6o TEXT-BOOK OF PHYSIOLOGY. 



forms. The thrombi which form on the surface of atheromatous ulcers, on 

 the valves of the heart, and in the veins in consequence of diseased states, on 

 threads or needles passed through the vessels, at the orifices of torn blood- 

 vessels, consist largely of blood-plaques. A thrombus so formed may con- 

 tain a number of delicate fibrin threads, which, however, present a different 

 appearance from the fibrin of the extra-vascular clot. In the thrombi which 

 form around foreign bodies there is a larger quantity of fibrin than in those 

 originating from causes wholly within the vessel. 



