THE IMPRINTING OF NUTRITIONAL DISTURBANCES ON THE GROWING BONE

Abstract

WHEN nutritional disturbances in the young animal become so severe that nutrient material is inadequate to go around, in the economy of nature the bones are sacrificed. Preference is given to those organs on which continued existence depends and, if they also suffer, they do not do so to a comparable extent. In the crisis the bones simply cease to grow and, when the crisis is over, proceed to carry on again as if nothing had happened. Nature's method of shedding the burden of the skeleton and, presumably, of the other extra-vital tissues in periods of nutritional stress leaves marks in the growing bones, as seasonal sapless periods leave their marks in trees in the form of rings and as the fasting spawning periods in the anadromous fishes record themselves by lines in the scales. Doubtless, the soft tissues of the locomotor system, like the bones, reflect these nourishment withdrawals, but the resulting cellular changes are not located in areas where they can be recognized and, moreover, are probably evanescent anyway. The marks in the trunks of trees, in the scales of fishes and in the growing bones of warm-blooded animals can be recognized because they are strung out seriatim, for the reason that linear growth takes place in increments, one superimposed upon another in the order of time, and also because the material is durable. Although growth arrest marks in the bones originate in the organic matrix, the matrix becomes immediately infiltrated with mineral matter so that the marks become petrified in situ, so to speak.