292 MIGRATION OF WHITE CORPUSCLES. [Book i- 



puscles, however, are not the only bodies present in the peri- 

 pheral zone. Though in the normal circulation blood-platelets 

 (see § 33) cannot be seen in the peripheral zone, and hence (on 

 the view, which has the greater support, that these bodies are 

 really present in quite normal blood) must be confined to the axial 

 stream, they make their appearance in that zone during the 

 changes which we are now describing. Indeed, in many cases they 

 are far more abundant than the white corpuscles, the latter appear- 

 ing imbedded at intervals in masses of the former Soon after 

 their appearance the individual platelets lose their outline, and run 

 together into formless masses. 



§ 161. This much, the appearance of numerous white cor- 

 puscles 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 obstruction 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 cor- 

 puscle, by what appears to be an example of amoeboid movement, 

 makes its way through the wall of the vessel 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 extent 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 fluid passes 

 from the interior of the blood vessels through the altered walls 

 into the lymph spaces more rapidly than it escapes from the 

 lymph spaces along the lymphatic channels ; these lymph spaces 

 become distended with lymph, which also changes somewhat in its 

 chemical characters ; it tends to clot more readily and more firmly, 

 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 

 inflammation. 



If the inflammation now passes off the white corpuscles cease to 

 emigrate, 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 themselves, though they may remain for a long time 

 dilated, eventually regain their calibre, and a normal circulation is 



