PRINCIPLES OF VETERINARY SURGERY 77 



endothelial cells, parasites, foreign bodies, shreds of. tissues, 

 etc. 



ETIOLOGY AND PATHOLOGY.— In the living 

 healthy blood flowing in healthy vessels the solid constitu- 

 ents are held in suspension or in solution. As Jong as- the 

 normal blood flows at a certain rate of speed and meets no 

 other object within the smooth endothelium of the intima, it 

 retains its liquid state, but when the current is stopped or 

 retarded, or the lining of the vessels becomes wounded" or 

 diseased, a certain amount of coagulation will promptly re- 

 sult. 



Thrombosis may be caused by slowing or arrest of the 

 blood current, , by pathological changes in the walls o£ the 

 blood vessels, or by changes in the blood itself. 



If the blood current in the heart, in the large vessels, or 

 in any local part becomes 'very slow^, the leucocytes adhere 

 to the intima and fibrin becomes deposited upon them. More 

 leucocytes impregnate the mass and more fibrin forms, until 

 the lumen of the vessels becomes small and even entirely ob- 

 literated with a firm clot that varies in color from yellow to 

 dark red, according to the number of leucocytes it contains. 



These thrombi often form very rapidly just before death, 

 and may be found to entirely fill up such large vessels as the 

 posterior aorta, the pulmonary arteries, the coronary arter- 

 ies, the brachial arteries, the carotids and the large veins. 

 The firmness of their organization would often suggest a 

 much slower process of formation. In the cavities of the 

 heart they are found with great frequency post-mortem, in 

 the form of free, elongated masses of whitish- coagula that 

 tear with some difficulty. The facts anent these throrribi are 

 that, they form during the few moments, or at least the few 

 hours, before death. The real ante-mortem thrombi that 

 have existed in the heart or blood vessels for some time be- 

 fore death are found adherent to the endothelial layer of the 



