INFLAMMATION AND LEUCOCYTE RESPONSE 5o 



is called the stage of red Juptitizatioh or liverlike ai)i)earaiice and 

 consistency of the lung. The microscopic picture at this stage 

 would show the alveolar walls thickened, the capillaries distended, 

 the alveoli filled with coagulated albuminous fluid, leucocytes, 

 mononuclear cells, bacteria, some red cells, and a great deal of 

 fibrin. 



The next stage is one described as "gray hepatization." The 

 red cells either lose their hemoglobin or are destroyed while the 

 lung remains otherwise the same. The last stage is that of resolu- 

 tion. Proteolytic enzymes of leucocytic origin (from leucocytes 

 that are destroyed) liquefy the coagulated proteins and the prod- 

 ucts are eliminated in the sputum and urine and the lung returns 

 to normal. The bacteria have been phagocytized by neutrophiles, 

 free mononuclear and fixed mononuclear cells. The phenomenon of 

 crisis which is generally regarded as peculiar to lobar pneumonia 

 in man has been experimentally duplicated by Goodner in his 

 "dermal pneumonia" (intradermal infection) in rabbits. 



(2) Furuncle. — Another interesting example of acute pyogenic 

 infection in man is the furuncle (boil) due to the staphylococcus. 

 Infection usually occurs around a hair follicle. Here one observes 

 hyperemia, exudation, the accumulation of fluid, leucocytes, red 

 cells, fibrinogen, and bacteria in the area of inflammation. Coagula- 

 tion of the protein occurs. There is a piling up of neutrophiles and 

 mononuclear cells at the outer margin of the spherical zone of 

 coagulation. The small blood vessels and lymphatics are injured 

 and become plugged with thrombi and hyaline plugs, respectively, 

 which tend to prevent the spread of the infection. 



In the furuncle the coagulated mass of cells dies. Here again 

 proteolytic enzymes of leucocytic origin begin to liquefy the coagu- 

 lated mass which in this case contains dead tivssue. Liquefaction 

 begins at the outer margin and progresses toward the center. The 

 liquefied tissue debris, dead and living leucocytes, bacteria, fibrin, 

 etc., constitutes the pus that one sees while the unliquefied central 

 portion is the "core" of the boil. The cavity thus formed is lined 

 with a membranous-like material made up of fibrin, various types 

 of white cells, tissue cells, etc., and is called the pyogenic membrane. 

 It, with its phagocytes and the hyaline and fibrinous plugs in the 

 lymphatics and blood vessels, acts as a protective barrier to the 

 spread of infection. 



