72 



CHANGES IN THE CIRCULATION OF THE BLOOD. 



usually alone suffice to induce 

 trausudatiou, although it may 

 favor its occurrence. 



The transuded fluid, called 

 transudate, is usually transparent 

 and colorless or yellowish ; it con- 

 tains the same salts as the blood 

 plasma, but less albumin. It may 

 contain fat, mucin, urea, biliary 

 acids, coloring-matter of the bile; 

 fibrinogeii is usually present in 

 variable quantity, and, rarely, 

 fibrin. It may contain endothe- 

 lial cells from the lymph spaces, 

 and a variable number of red and 

 white blood cells. The amount of 

 fluid which may accumulate in the 

 tissues varies greatly, depending 

 upon whether they are loose or 

 dense in texture. The fibres and 

 cells of loose tissues may be 

 crowded widely apart; the cells 

 are apt to be more granular than 

 normal, they may contain droplets 

 of fluid or they may be atrophied. 

 Transudates occurring in inflam- 

 mation usually contain a consid- 

 erable number of white blood cells and more or less fibrin, and differ in 

 this from the uon- inflammatory transudations ; but in some cases there 

 is no sharp distinction between them. The inflammatory trausudates 

 are often called exudations or exudates. 



FIG. 8. OCCLUDING THROMBUS OF THE ILIAC. 

 The vessel is laid open, showing the lamellated clot. 



Thrombosis and Embolism. 



THROMBOSIS. 



Thrombosis is a coagulation of blood in the heart or vessels during 

 life. The coagulum is called a thrombus. Thrombi may lie against the 

 wall of the vessel, only partially filling the lumen, and are then called 

 parietal thrombi ; or they may entirely fill the vessel, and are then called 

 occluding thrombi (Fig. 8). 



The thrombus may form first upon the wall, and by more or less con- 

 tinuous deposit of fresh material, may extend, usually but not always, in 

 the direction of the blood current, either as a parietal or an occluding or 

 obstructing thrombus along the vessel or into connecting channels. 



Thrombi may occur as the result of an injury to the wall of a vessel, 

 or may follow its compression or dilatation ; they may result from some 

 alteration of the wall of the vessel by disease or by the retardation of the 



