136 ANATOMY FOR NUKSES. [CHAP. XI. 



arriving on the scene, the inner surface of the veins and cap- 

 illaries soon become lined with a layer of these cells. Now, 

 though the vessels still remain dilated, the stream of blood 

 begins to slacken, and the white corpuscles lying in contact 

 with the Avails of the vessels are seen to thrust themselves 

 through the distended walls into the lymph spaces outside. 

 This migration of the white cells is accomplished by means of 

 their amoeboid movements. They thrust elongated processes 

 through the walls, and then, as these processes increase in size, 

 the body of the cell passes through into the enlarged process 

 beyond, the perforation appearing to take place in the cement 

 substance between the endothelial cells forming the walls of 

 the vessels. Through this migration, the lymph spaces around 

 the vessels in the inflamed area become crowded with white 

 corpuscles. At the same time the lymph not only increases in 

 amount, but changes somewhat in its chemical characters : it 

 becomes more distinctly and readily coagulable, and is some- 

 times spoken of as "exudation fluid." This change of the 

 lymph with the increased quantity, together with the dilated 

 crowded condition of the blood-vessels, gives rise to the swell- 

 ing which is one of the features of inflammation. 



If the inflammation now passes away, the white corpuscles 

 cease to emigrate, cease to stick so steadily to the sides of the 

 vessels, the stream of blood quickens again, the vessels regain 

 their ordinary caliber, and a normal circulation is re-established. 

 But this inflammatory condition, instead of passing off, may go 

 on to a further stage ; and, if this is the case, more and more 

 white corpuscles, arrested in their passage, crowd and block the 

 channels, so that, though the vessels remain dilated, the stream 

 becomes slower and slower, until at last it stops altogether, and 

 stagnation or " stasis " sets in. The red corpuscles, in this con- 

 dition of things, are driven in among the white corpuscles, the 

 vessels are filled and distended with a mingled mass of red and 

 white corpuscles, and it may now be observed that the red cor- 

 puscles also begin to find their way through the distended and 

 altered walls of the capillaries into the lymph spaces outside. 

 This is called the diapedesis of the red corpuscles. 



This stagnation stage of inflammation may be the beginning 

 of further mischief and of death to the inflamed tissue, but it, 

 too, may like the earlier stages, pass away. 



