On the metabolic gradient of the frog's egg

Abstract

After a very considerable amount of work, chiefly on regeneration of certain hydroids and flatworms, Child came to the conclusion that in the adult forms there is a gradient in the rate of metabolism extending from a region of high rate at the anterior end to a region of low rate at the posterior end. On this basis he was able to predict with a remarkable degree of success many results which might be obtained in experimental work on regeneration in these forms. As a further result he enunciated his “Dynamic Conception of the Individual.” In this conception he postulates that in all organisms there is a gradient in the rate of metabolism from a dominant region of high metabolic rate to regions of a lower rate. In axiate organisms this dominant region is at the anterior or apical end, and the rate of metabolism decreases towards the posterior or basal end. These gradients are evidenced in a variety of ways. There may be an apico-basal gradient in the rate of cell division in a cleaving egg or in the rate of morphogenesis, the organs of the apical end developing before those of the basal end. There is often a gradient in the ease with which intra vitam stains will stain the various regions of the organism. There may be a gradient in electric potential, or in the susceptibility of the organism to toxic agents.