518 



SCIENCE 



[N. S. Vol. XLIII. No. 1111 



localization of these conditions at a greater 

 distance. 



The relation of the central nervous sys- 

 tem to the axial metabolic gradients is a 

 point of particular interest. The apical or 

 cephalic part of the nervous system devel- 

 ops from the apical region of the major axis 

 which is, at least primarily, the region of 

 highest rate in the whole body and the post- 

 cephalic portions develop in or near the 

 region of highest rate in the symmetry gra- 

 dients, the median ventral region in the bi- 

 lateral invertebrates, the median dorsal 

 region in the vertebrates. 



If the organic individual consists pri- 

 marily of a number of qualitatively differ- 

 ent entities between which chemical trans- 

 portative correlation exists, it is difficult to 

 understand why it should transform itself 

 during development into an individual 

 which is dominated by a nervous system, in 

 which transmitted changes instead of trans- 

 ported substances are the means of correla- 

 tion. From this point of view the nervous 

 system seems to arise from nowhere and 

 out of nothing as an added superior system 

 which integrates the previously existing 

 mosaic of entities or qualities into an indi- 

 vidual. From the dynamic viewpoint, ac- 

 cording to which a physiological axis is 

 primarily a metabolic gradient, the ap- 

 pearance, localization, course of develop- 

 ment and functional dominance of the cen- 

 tral nervous system are the natural and nec- 

 essary consequences of the relations of 

 dominance and subordination which have 

 existed in the axial gradients from the 

 beginning. The central nervous system is 

 in fact merely the final morphological and 

 physiological expression of dynamic rela- 

 tions which constitute the first step in indi- 

 viduation. 



Brief mention of some other cases of func- 

 tional dominance in relation to metabolic 

 gradients is perhaps of interest. Mayer has 



shown that in the medusa Cassiopea that 

 particular one of the marginal nerve centers 

 which has the most rapid rhythm initiates 

 the wave of muscular contraction and for 

 the time being sets the pace for the others. 

 Dominance here is of course only tempo- 

 rary. In the vertebrate heart the sinus 

 region is dominant and initiates the beat. 

 Dr. Hyman has been able to demonstrate 

 that in the tubular embryonic heart an axial 

 metabolic gradient exists and the region of 

 highest rate in this gradient develops into 

 the sinus. Tashiro has recently shown that 

 a metabolic gradient exists in the neuron 

 and that conduction of impulses is normally 

 down this gradient. 



Fifth, the localization of, and the condi- 

 tions determining, various processes of 

 agamic reproduction of new individuals 

 from parts of those previously existing 

 afford valuable evidence in support of the 

 dynamic conception of the individual. 

 Since the transmitted changes in proto- 

 plasm undergo a decrement in effectiveness 

 with increasing distance from the point of 

 origin, their range of effectiveness, in other 

 words the range of dominance, is spatially 

 limited. This range may vary with differ- 

 ent conditions, metabolic rate in the domi- 

 nant region, intensity of transmitted excita- 

 tion, conductivity of protoplasm, interfer- 

 ence with other transmitted excitations, etc. 

 The range of dominance in a particular 

 axis in a specific protoplasm under given 

 conditions represents the physiological 

 maximum of size which the individual can 

 attain in that dimension under those condi- 

 tions and remain physiologically an indi- 

 vidual. Any part which comes for any rea- 

 son to lie outside the range of dominance is 

 thereby physiologically isolated and no 

 longer i^hysiologically a part of the indi- 

 vidual. In most plants and lower animals 

 such physiological isolation of a part, like 

 physical isolation, is usually followed by 



