Inflamation. P/ogosis. Phlegmasia. 49 



the chemiotaxis of the leucocyte for the invading germ, the num- 

 ber of white cells that emigrate into the inflamed tissue and en- 

 gage in the work of phagocytosis, and on whether the particular 

 animal system and its white cells have sustained a previous at- 

 tack by the same germ and has thereby been educated to produce 

 a greater amount of the defensiv^e proteids (leucomaine, anti- 

 toxin, enzyme) than it naturally would (acquired immunity). 



Even with an abundant emigration of the leucocytes into the 

 inflamed or invaded tissue, a number, greater or less, are usually 

 destroyed by the bacterial poisons and pass into degeneration or 

 liquefaction, as in the formation of pus, and yet the attacking germ 

 may be overcome, destroyed and devoured by the rapidly increas- 

 ing survivors. In general terms the migration of the cells is in 

 inverse ratio to the susceptibility of the animal to the microbe or 

 the disease which it causes. 



The positive and negative chemiotaxis, which determine phago- 

 cytosis or prevent it, may be seen in the action of the leucocytes 

 toward the germs of two diseases, to one of which the animal is 

 susceptible and to the other of which it is not. Thus the leuco- 

 cytes of the pigeon take in the bacillus anthracis and suffer noth- 

 ing apparently, whereas the same white cells of the dove are re- 

 pelled by the bacteria of fowl cholera which are not therefore 

 found in their interior. 



The leucocytes that migrate from the bloodvessels are in the 

 main, the most numerous, (the neutrophile or polynuclear) form ; 

 the mononuclear leucocytes with horseshoe shaped nucleus also 

 migrate but in much fewer numbers and are as a rule less oc- 

 cupied in phagocytosis. At the same time, these two forms may 

 show each a preference for a particular microbe, the polynuclear 

 cell sometimes devouring one which the mononuclear cell rejects, 

 and the mononuclear cell taking in one which the polynuclear re-- 

 fuses. 



The small round white cells (lymphocytes) and the eosinophile 

 leucocytes take no prominent part in phagocytosis. 



EXUDATION. 



In inflamed vascular tissues one of the most important results 

 is the exudation. This is not, however, a mere transudation of 



