The rate of bony tissue deposition in the spongiosa of the extremities of long bones in the dog.
9 mongrel dogs ranging from 5 months to 3 years of age were given 3 single endovenous Alizarin injections at 20-day intervals. In transverse sections of the epiphyses and metaphyses of the proximal and distal ends of the femur, tibia, radius and humerus, we measured the thickness of the bony tissue newly formed during the period between the 1st and 2nd Alizarin administration, and separately of that laid down between the 2nd and the 3rd. The weighted means and histograms set up by us of the values severely gathered in the tubular (peripheral) and lamellar (deeply placed) spongiosa in each metaphyseal and epiphyseal sections, are the expression of the mean linear rate of bony tissue deposition. The mean linear rate of bone deposition (1) declines with age; (2) is higher in the metaphyses than in the epiphyses; (3) in single metaphyses it is higher in the tubular than in the lamellar type of trabeculae. These differences are much marked in the animals undergoing body growth, tending to become appreciably reduced in adult specimens. Significant differences in bone deposition rates between corresponding regions of different bones from the same individual were not seen to occur. The differences in bony tissue deposition rate between the tubular and lamellar spongiosa networks seem to depend upon the action exerted by local factors functionally closely associated with the remodelling of metaphyses during growth in length of the skeletal segments, hence upon predominantly mechanical factors.