1) The viscosity of the intrapleural blood and effusion after resection of the lung was measured using Hess-Erma's Viscosimeter. 2) Aspirating the viscous liquid in the pleural cavity is to be performed with "the Law of Poiseuille". 3) The length of radius of drainpipe influences mostly on the aspiration. The appropriate length of the inside diameter is from 0.7 cm to 0.9 cm. 4) The drainpipe must to be seamless from the pleural cavity to the bed and as short as possible, and the shape of its tip must to be simple. 5) So long as the air leakage from the lung continues, "Y" type tube is not adequate. 6) The appropriate number of the side holes is one or two and the appropriate position sits within 3 cm from the tip. 7) The appropriate pressure of the aspiration is from -10 to -15 cm H(2)O. 8) "Three bottle catheter suction drainage consisting of a trap bottle, water seal and valve bottle in series" is favourable for the aspiration apparatus. 9) The air leakage continues for about 10 hours at soonest. The air leakage stops in 15 hours to 50 hours mostly, but not a few continue for more than 65 hours.