234 THE VASCULAR MECHANISM. 



be seen in the peripheral zone, and hence must be confined (on the view, 

 which has the greater support, that these bodies are really present in quite 

 normal blood) to the axial stream, they make their appearance in that 

 zone with the changes which we are now describing. Indeed, in many cases 

 they are far more abundant than the white corpuscles, the latter appearing 

 imbedded at intervals in masses of the former. Soon after their appearance 

 the individual platelets lose their outline and run together into formless 

 masses. 



169. This much, the appearance of numerous white corpuscles and 

 platelets in the peripheral zones may take place while the stream, though 

 less rapid than at the very first, still remains rapid ; so rapid at all events 

 that, owing to the increased width of the passages, in spite of the obstruc- 

 tion offered by the adherent white corpuscles, the total quantity of blood 

 flowing in a given time through the inflamed area is greater than normal. 

 But soon, though the vessels still remain dilated, the stream is observed 

 most distinctly to slacken and then a remarkable phenomenon makes its 

 appearance. The white corpuscles lying in contact with the walls of the 

 veins or of the capillaries are seen to thrust processes through the walls ; 

 and, the process of a corpuscle increasing at the expense of the rest of the 

 body of the corpuscle, the whole corpuscle, by what appears to be an ex- 

 ample of amoeboid movement, makes its way through the wall of the ves- 

 sel into the lymph space outside ; the perforation appears to take place in 

 the cement substance joining the epithelioid plates together. This is the 

 migration of the white corpuscles to which we alluded in 32, and takes 

 place chiefly in the veins and capillaries, not at all or to a very slight ex- 

 tent in the arteries. Through this migration the lymph spaces around the 

 vessels in the inflamed area become crowded with white corpuscles. At the 

 same time the lymph in the same spaces not only increases in amount but 

 changes somewhat in its chemical characters ; it becomes more distinctly 

 and readily coagulable, and is sometimes spoken of as " exudation fluid," 

 or by the older writers as " coagulable lymph." This turgescence of the 

 lymph spaces, together with the dilated, crowded condition of the blood- 

 vessels, gives rise to the swelling which is one of the features of inflam- 

 mation. 



If the inflammation now passes off the white corpuscles cease to emi- 

 grate, cease to stick for any length of time to the sides of the vessels, the 

 stream of blood through the vessels quickens again, and the vessels them- 

 selves, though they may remain for a long time dilated, eventually regain 

 their calibre, and a normal circulation is re-established. The migrated cor- 

 puscles move away from the region, along the labyrinth of lymph spaces, 

 and the surplus lymph also passes away along the lymph spaces and lym- 

 phatic vessels. 



170. The condition of things, however, instead of passing off may go 

 on to a further stage. More and more white corpuscles, arrested in their 

 passage, crowd the channels and block the way, 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 are 

 driven in, often in masses, among the white corpuscles and platelets, the 

 distinction between axial stream and peripheral zone becoming lost; and 

 arteries, veins, and capillaries, all distended, sometimes enormously so, are 

 filled with a mass of mingled red and white corpuscles and platelets. 

 When actual stagnation occurs the red corpuscles run together so that 

 their outlines are no longer distinguishable ; they appear to become 

 fused into a homogeneous red mass. And it may now be observed that, 

 not only white corpuscles but also red corpuscles make their way through 



