The collagen fibrils in fowl medullary bone

Medullary bone from the femurs of laying fowls was examined by electron microscopy, with particular reference to the nature and environment of its collagen fibrils. The collagen fibrils appeared to have a preferred orientation along the long axis of the bone. There were no clear‐cut cyclic changes in the fibril diameters during egg calcification. The tissue was rich in mucopolysaccharides, visualised as strands or sheets connecting the fibrils. Lysis of the fibrils appeared to be associated with osteoclasts rather than osteocytes.