348 A. \V. BELLAMY. 



to modify and control development on a predictable basis. 1 

 Child looks upon a physiological axis in its simplest terms as a 

 quantitative gradation in physiological condition. He has 

 brought forward evidence from a number of sources which point 

 to the conclusion that this gradient is a gradation in rate of 

 metabolism, or at least of certain fundamental reactions such 

 as the oxidation-reduction processes, which is associated with a 

 gradation in the physical condition and constitution of the 

 protoplasm. 



If a gradient in physiological condition is a fundamental 

 ordering factor in the process of physiological axiation, it should 

 be possible to obtain as many expressions of this gradient as 

 there are aspects into which fundamental metabolic activity and 

 the physical constitution of the protoplasm may be analyzed. 

 Hence, we might expect to find, e.g., gradients in irritability; 

 in growth and differentiation and development; in the visible 

 morphological condition of the protoplasm; in permeability; 

 in the active mass of enzymes; in electrical potential; in oxida- 

 tion as measured by oxygen consumption and in carbon dioxide 

 production; and conversely, gradients in susceptibility to lack 

 of oxygen. Well known biological facts afford demonstrative 

 evidence for the existence of some of these gradients. Further 

 evidence for the existence of other of these gradients has been 

 published by Child, Hyman, et al. 1 Other evidence is yet 

 unpublished. 



"All the various lines of evidence considered agree in showing 

 that axial gradients in the dynamic processes are characteristic 

 features of organisms and that a definite relation exists in each 

 individual between the direction of the gradient in any axis and 

 the physiological and structural order which arises along that 

 axis. In the major axis the region of highest rate in the meta- 

 bolic gradient becomes the apical or anterior region of the 

 individual, and in the minor axes also the regions of highest rate 

 in the gradients represent particular features of the order in 

 each case. Along any axis particular parts apparently represent 

 particular levels in the gradient. The variety, extent, and agree- 



1 See footnote i, page 315. 



