78 PRINCIPLES OF VETERINARY SURGERY 



vessel or cavity containing them. In the heart they adhere to 

 the valves. The free ones are all of rapid formation. The so- 

 called "chicken-fat" thrombus abounds with leucocytes and 

 contains few red blood corpuscles, while in the "current- 

 jelly" variety the opposite condition e3(;ists. These two varie- 

 ties may co-exist in any given thrombus of rapid formation, 

 the first layer around the intima being whitish and the re- 

 mainder jelly-colored. The clot that forms just before death 

 or immediately after may be either whitish or dark, but it is 

 always stringy, quite firm and elastic, while the slow forming 

 ante-mortem clot is always whitish and possessed of a char- 

 acteristic friability. 



The changes in the blood vessels that favor thrombosis 

 are inflammations of bacterial or traumatic origin. These 

 cause an erosion or wrinkling of the intima and thus lead to 

 the accumulation of leucocytes and then fibrin upon the al- 

 tered area. A trivial lesion may produce a clot of large di- 

 mensions by supplying the nucleus upon which more and 

 more blood coagulates until the vessel is obturated a consid- 

 erable distance from the initial lesion. Aneurisms in the same 

 manner are very prone to cause the formation of thrombi. 

 The ligation of blood vessels in surgical operations always 

 causes the formation of a clot in the ligated stump, which 

 may extend into the main trunk and thus lead to a very ex- 

 tensive coagulum. 



The blood itself may be altered so as to provoke the for- 

 mation of thrombi by the accidental introduction of foreign 

 matter into the blood current. Medicaments administered in- 

 travenously, air accidentally admitted into a vein, pus ab- 

 sorbed from a suppurating focus, and micro-organisms and 

 their products, may readily cause the blood to coagulate 

 within the vessels. And finally one thrombus may lead to 

 the formation of others. Particles become detached (em- 



