1 . Sloughing of homogenous skin grafts and clouding of corneal transplants have been shown to be due to antigen-antibody reaction; antigens A and B have been demonstrated in human epidermis and corneal tissue; and anti-red-cell agglutination has been observed in dogs after homogenous bone transplantation. Human bone was therefore examined in thirty-three experiments to determine the presence or absence of A and B antigens.

2. The bone was separated into hard cortical bone, hard washed cancellous bone and soft-tissue washings of bone.

3. Adsorption experiments showed that A and B antigens are absent from cortical bone. A and B antigens are present in cancellous bone.