In a companion paper, in which I reported seven cases of milky effusion and described the so-called pseudochylous fluid from each, it was pointed out that there was disagreement as to the cause of the turbidity of such fluids, and as a consequence much confusion among the descriptive terms applied. Some writers hold that emulsified fat is the cause; others, finding very little fat, are unwilling to ascribe turbidity to amounts so insignificant; and still others, finding no fat, ascribe turbidity to an unknown protein or some uncommon substance, such as glucoprotein, mucinoids, or a lecithin-globulin complex. The present work was undertaken with the hope of throwing further light on the subject by investigation into the nature of the turbidity in five of seven fluids described in the previous paper. The results were clearcut. Emulsified fat was proved in all five cases to be the cause of turbidity.