PRINCIPLES OF VETERINARY SURGERY 79 



boli) and then float to other parts of the body and there form 

 new thrombic foci. 



TERMINATIONS AND EFFECTS— Thrombi may 

 become organized, that is, they may be replaced with con- 

 nective tissue through the activity of the endothelial cells 

 which perform the function of fibroblasts. In this event the 

 vessel becomes permanently obliterated. Its lumen is filled 

 with a firm fibroconnective tissue that will henceforth per- 

 manently obstruct the channel. Striking examples of this 

 termination are found in the iliac arteries of horses, because 

 of which seizures of very transient but of very acute lameness 

 may occur in one or both hind-legs. Again, thrombi may 

 liquefy and restore the vessel to its normal condition, they 

 may undergo septic disintegration with results varying with 

 the nature of the infection, they may calcify or they may be- 

 come detached and float away as emboli and then create new 

 thromboses. Finally, they may produce gangrene by ob- 

 structing the blood supply to any given part, or abscess by 

 becoming infected at the initial seat or by the floating of 

 infected emboli to remote regions. Thus embolic pneumonia 

 may readily result by the flow of a septic embolus from a 

 peripheral trauma through the veins to the capillaries of the 

 lungs. 



The thrombus retains its original condition for a very 

 brief period only. It is no sooner formed than changes begin 

 to occur. ,,At first soft as any ordinary clot of blood it soon 

 becomes firm, fibrous, softened, granular, calcified or puru- 

 lent. 



The effect of thrombi and emboli depends upon the im- 

 portance .of the vessels concerned and the nature of the clot. 

 If infected they are always more serious than when micro- 

 organisms do not enter into the process of their formation. 

 Wide-spread oedema of an entire extremity, circumscribed 

 or ciififused gangrene, multiple abscesses, embolic pneumonia, 



