Studies on the skeletal tissues. 5. The influence of age upon the degree of calcification and the incorporation of 32P in bone

Abstract

The degree of calcification (Ca/N ratio) of cortical bones in rabbits increases from about the 5th day of life and in the cat from about the 9th day of life. From the birth of kittens until they are 9 days old there is a continuous reduction in the degree of calcification. The calcification of the cancellous bone in rabbits remains approximately constant during the whole of growth, whereas in cats this bone becomes less calcified during growth. The amount of P32 incorporated during the 4 hours following administration declines throughout the growth of rabbits in both cancellous and cortical bone. In cats there is a maximum incorporation in both types of bone at an age of about 14 days, being more marked in cancellous bone. In both cats and rabbits there is a very marked change during growth in the incorporation of P32 in the subperiosteal and endosteal layers of bone. The incorporation of P32 in the former layers declines throughout growth, whereas that in the latter layers reaches its maximum in the adult.