Congestion		Progressive disintergration of red cells and persistence of fibrinosuppurative exudate.
Red Hepatisation		Exudates undergoes progressive enzymatic digestion producing semifluid debris that is resorbed
Gray Hepatisation		Vascular engorgement, intra-alveolar fluid with few neutrophils, numerous bacteria
Resolution		Exudation with neutrophils, red cells and fibrin filling alveolar spaces - appears red, firm and airless