580 DISEASES OF THE ARTERIES AND LYMPHATICS. 



with those of the occluded vessels. The want of circulation is 

 scarcely shown during repose ; there seems to be but a slight 

 degree of muscular debility ; but when the animal is compelled 

 to move, he immediately exhibits signs of inability. 



Virchow, in his w^ork on Cellular Patliology, describes the 

 process of the coagulation of the blood in the vessels under the 

 term " thrombosis^ A clot so formed he calls a thrombus, and 

 the impulsion or projection onward of a clot or thrombus, 

 detached from the walls or valves of the vascular system, is 

 described by him under the term " embolism." 



Thrombi may be propelled from the heart to the arterial 

 peripheric vessels, or they may form in veins and travel to the 

 heart. 



He says : — " As long, however, as the thrombus is confined 

 to a branch vessel, so long the body is not exposed to any 

 particular danger ; the worst that can happen is, that, in con- 

 sequence of a peri or meso phlebitis, an abscess may form and 

 open externally. Only, the greater number of thrombi in the 

 small branches do not content themselves with advancing up to 

 the level of the main trunk, but pretty constantly new masses 

 of coagulum deposit themselves in the blood upon the end of 

 the thrombus, layer after layer; the thrombus is prolonged 

 beyond the mouth of the branch into the trunk in the direction 

 of the current of the blood, shoots out in the form of a thick 

 cylinder farther and farther, and becomes continually larger 

 and larger. Soon this prolonged thrombus no longer bears 

 any proportion to the original thrombus from which it proceeds. 

 From a lumbar vein, for example, a plug may extend into the 

 vena cava as thick as the last phalanx of the thumb. 



" It is these prolonged plugs that constitute the source of 

 real danger, as the stream of blood may detach minute portions, 

 hurry them away with it, and wedge them tightly into the 

 nearest system of arteries or capillaries. 



" Many cases of sudden death that would otherwise be 

 inexplicable, are thus accounted for." The question is one of 

 importance to the veterinarian, and is well worthy of further 

 study. 



In the human subject clots occasionally originate from very 

 trivial local causes, chilblains even being the starting-point. 



