The effects of changes in the environmental temperature on the growth of bone in the mouse. Radiological and morphological study.

Groups of 25-day-old mice were kept at 33 degrees, 21 degrees and 8 degrees for up to 195 days. Measurements and observations on length, width, gross and microscopic structure using radiological and histological techniques were made on central and peripheral bones. Tail bones of animals kept at 33 degrees grew longer and faster than those in the cold but also closed their epiphyses earlier. The diaphyses of "hot" vertebrae were cylindrical but "cold" and "control" vertebrae were of narrower diameter in their mid-diaphyses compared to their distal ends producing a "waisted" appearance. The "cold" vertebrae in addition showed thickened cortical bone and more woven bone in the marrow cavity. These changes were interpreted as indicating a disproportionate sensitivity of external apposition of cortical bone to cold. The internal remodelling of bone as the vertebrae grew was only affected by the coldest conditions and accounted for the thickened cortex and denser woven bone in the marrow cavity.