It is rather remarkable that so many of the profession continue to associate this term with congenital heart disease, although the expression itself merely refers to that peculiar lividity of the skin that occasionally supervenes some little time after birth. Theoretically considered, it might be dependent on anything which would interfere with the proper oxygenation of the blood. Thus, general venous stasis, from whatever cause, or a diminished amount of normally-working lung tissue, would act as causal factors just as readily as would any interference with the bringing of venous blood from the right heart, as for instance narrowing of or obstruction in the pulmonary artery. Indeed, Smith regarded cyanosis as a blood disease due to lack of oxygenation or an excess of carbonic acid, and as such ranked it among blood diseases proper, as leukemia. When due, however, to cardiac lesions, the most prominent cause has not been, as