262 



Inflammation. 



distension of the blood vessels, hypersemia. In the exposed or irri- 

 tated parts there may be first observed a dilatation of the arteries 

 and later of the capillaries and veins. With this the blood current 

 is first accelerated, but with the occurrence of dilatation of the veins 

 of the tissue the circulation becomes slowed. Here or there it may 

 stop for a variable period, and the corpuscles which previously 

 were forced along in the central part of the stream become dis- 

 tributed uniformly throughout the lumen of the vessel in the stag- 

 nating blood. In addition the delicate capillaries, through which 

 previously plasma mainly flowed with here and there a blood cell, 

 are found engorged with blood corpuscles. With this slowing of 

 the current the sluggishly moving white blood cells tend to collect 



A 



a 





■iS-'- 







Fig. 48. 



Various steps iu the passage of a white blood corpuscle through the wall of a 

 vessel. On the left of the short lines which represent the vessel walls, is 

 supposed to be the intravascular blood; on the right the tissue; X 1,0"0. 

 (After Thoma.) 



more and more on the inner surface of the vessel wall, giving rise 

 to the so-called marginal deposition of the white corpuscles, and as 

 additional ones are continually added from the blood the capillaries 

 may, from their increasing accumulation, be found completely oc- 

 cluded by leucocytes. There may next be observed a very charac- 

 teristic feature, the exudation or emigration from the vessels of 

 large numbers of the white corpuscles into the area of inflammation. 

 These motile amoeboid cells, which were more or less flattened 

 against the internal surface of the vessel, penetrate the capillary or 

 venous walls by protruding a pseudopod-like process of their pro- 

 toplasm through it (mainly at the cement lines between the endo- 

 thelial cells) the rest of the protoplasm following in a distinctly 



