The absorption of calcium (Ca) and factors which influence it have been reviewed by L. H. Alien. Both active transport and diffusion are important in the absorption process. Co was included in the studies of F. A. Suso and H. M. Edwards in which the absorption of several minerals was determined by the whole body counting technique after administration of the radioactive isotope to chickens. As with other minerals, the role of phytic acid or the fiber in the bran fraction to influence Ca availability is stili not clear. A number of plant components influence the availability of calcium. The level of oxalic acid in food has been a nutritional concern since calcium oxalate is extremely insoluble. Similarly, oxalic acid at 1% of the diet depressed growth, bone ash, and breaking strength at 0.9% Ca, but the effects were corrected by increasing the Ca. Ca absorption in humans is also enhanced by lactose.