There are various conditions which may give rise to a deficiency of blood in the lungs. It may depend: a. On exhausting hemorrhages.

b. On wasting of the blood, consequent on various acute and chronic diseases.

c. On the inspissation of the blood, consequent on rapid and great loss of serum, and on the inability of the blood, in this condition, to enter the capillaries; this is especially the cause of the anaemia of the lungs in Asiatic cholera.

d. Finally it occurs in association with pulmonary atrophy, with emphysema, and with the higher degrees of compression of the lungs.