Growth of the cartilages of the mid-line cranial base: a radiographic and histological study.

The importance of controlling litter size in growth studies is verified for Rattus norvegicus. A method of studying growth of the cranial base bones in the median sagittal plane is described and figures for growth rate in micrometres per day have been produced for the age range 4-480 days. The age range 4 to 80 days is identified as the period when 50% of growth takes place and therefore as a period which is particularly useful for growth studies. The presence of a caudorostral gradient in growth rate is suggested by the results. The nomenclature of the cell zones in endochondral growth sites is reviewed and the use of the term matrixogenic is offered to describe and identify more accurately one of the functional zones in endochondral growth sites.