PERNICIOUS ANEMIA
ETIOLOGY
The mechanism of the development of pernicious anemia has been explained by Castle1 on the basis of interaction of an "intrinsic factor" secreted by the gastric mucosa and an "extrinsic factor" provided by the diet, thereby producing a substance which controls the maturation of red blood cells in the bone marrow. Greenspon2 has performed experiments which in his opinion suggest a different interpretation of the observations of Castle. Greenspon's theory is as follows: It is assumed that an erythrocyte-stimulating hormone is secreted by the gastric mucosa. When pernicious anemia develops there is a loss of this hormone, coincident with atrophy of the gastric glands, and the anemia of the disease develops. In support of his theory this investigator reported that the injection of extracts of gastric mucosa of the hog into rabbits and guinea-pigs caused (1) a substantial increase in the number of circulating erythrocytes,