EMBOLIA PROLONGED THROMBI AND THEIR IMPORT. 239 



may form and open externally. Only the greater num- 

 ber of the 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 de- 

 posit themselves from 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 (Fig. 71, f) no longer bears any proportion to 

 the original (autochthonous) thrombus (Fig. 71, c), from 

 which it proceeded. The prolonged thrombus may have 

 the thickness of a thumb, the original one that of a knit- 

 ting-needle. From a lumbar vein, for example, a plug 

 may extend into the vena cava as thick as the last pha- 

 lanx of the thumb. 



FIG. 71. 



It is these prolonged plugs that constitute the source 

 of real danger ; it is in them that ensues the crumbling 

 away which leads to secondary occlusions in remote ves- 

 sels. They are the parts from which larger or smaller 



Fig. 71. Autochthonous and prolonged thrombi, c, c'. Smallish, varicose, lateral 

 branches (circumflex veins of the thigh), filled with autochthonous thrombi which 

 project beyond the orifices into the trunk of the femoral vein. t. Prolonged 

 thrombus produced by concentrically apposed deposits from the blood, t'. Pro- 

 longed thrombus, as it appears after fragments (emboli) have become detached from 

 it. 



