STRUCTURAL CHANGES DUE TO DAMAGE. 



299 



Thus, two influences appear to check the flow of the blood after 

 the inflammatory process has been inaugurated : (1) a diminution 

 of the pressure urging the blood forward, and (2) an increase in the 

 resistance offered to the passage of the blood through the smaller 

 vessels. To these, another factor increasing the resistance is added 

 as soon as the current has become slowed beyond a certain point. 

 During the normally rapid flow of the blood the corpuscles it con- 

 tains, being heavier than the serum, form a column in the axis of 

 the vessels, with a clear zone of serum around it (Fig. 264). This is 

 in accordance with the physical laws governing the behavior of sus- 

 pended particles in fluids circulating in a tube ; but if the rate of 

 flow be diminished beyond a certain point, the suspended particles 



FIG. 264. 



FIG. 265. 



.1 



FIG. 266. 



c d 



Positions of the corpuscles in circulating blood. (Eberth and Schimmelbusch.) 



Fig. 264. Appearance when the velocity of the circulation is normal : a, axial column of 

 corpuscles, both red and white, in such rapid movement that individual corpuscles can- 

 not be distinguished. Occasionally a white corpuscle is thrown from the axial mass and 

 appears in the plasmic zone, b. 



Fig. 265. Appearance when the velocity of the circulation is moderately reduced. The 

 zone b contains numerous leucocytes. 



Fig. 266. Appearance when the current of blood is sluggish: a, red corpuscles, still in the 

 axis ; b, peripheral zone, containing leucocytes, d, and blood-plates, c. 



When stasis is fully established the red corpuscles also invade the peripheral zone. 



The figures are from observations made on the vessels of a dog's omentum during life. 



invade the fluid zone at the periphery of the current, those which are 

 specifically most nearly of the same weight as the fluid passing 

 most freely into it. In the case of the blood those particles are the 

 leucocytes, which are lighter than the red corpuscles, and, as the 



