2i 8 BIOLOGICAL PHYSICS 



iibral nervous system, so to speak, is established, as the 

 primordial, or original, cell undergoes mitosis, whereby, 

 every added cell continues correlated to, and innervated 

 by, that cell, or the communal, or multi-cell, centre, 

 through the connected, or inter-cell processes, left by, and 

 maintained in, structural continuity with the various 

 sections of the mitosing cell, cells, and cell groups, to 

 their peripheral boundaries, or to their full structural 

 extent (see Fig. 77). 



From this point, in the process of evolution of the 

 nervous system proper, as the vital activities and neces- 

 sities of living things increase, and the conditions of 

 independent existence become more complex, it is ob- 

 served that vital energy is allowed to " play at large " less 

 and less, and that channels, strands, or filaments are 



FIG. 78. A. SECTION THROUGH PART OF A BILAMINAR BLASTODERM OF 

 THE CAT. (E. A. S.) 



ect., ent., ectoderm, entoderm ; z.p., thinned out zona pellucida. 



provided, along which it can pass with greater ease and 

 precision, and through which it can be operated by central 

 control, according to the dynamic necessities of the indi- 

 vidual structural elements of the increasingly complex 

 organisms. Here, we see the origin and evolution, or 

 development, of the first great nervous system so called, 

 viz. the sympathetic nervous system (Fig. 78). From 

 our earlier remarks on nerve energy, or life, we might, 

 however, correctly call the sympathetic nervous system 

 the second nervous system, inasmuch as the uni-cell 

 organisms are kept alive, or innervated, by molecular 

 continuity and intra-cell connective processes, and, there- 

 fore, by "0 nervous system" and, of necessity, the first 

 nervous system connected with the living protoplasm and 

 primary organisation of living forms generally. While 

 this is, no doubt, correct, for convenience' sake, we shall 

 entitle the sympathetic nervous system the first great 



