Hullin 47: The Telling Colors of Blood

Rulings by Rava: Issues of the lungs, specifically with regard to the lobes. Plus, Meimar, who answers the halakhic questions differently from Rava. Until the Gemara establishes that their answers pertain to different cases -- regarding the lobes. The sages are very precise here in their examination of the different concerns. Also, the implications of various colors -- dark grey (kosher) vs. black (not kosher) vs. green (kosher) vs. red (kosher) vs. Black being the shift from the red of blood, as it deteriorates, which means there's a problem in the lung that would lead to the color black. Plus, the stories of Rabbi Natan, who saves a couple of babies by advising their mothers to let the children's blood to be reabsorbed before brit milah (circumcision).