234 



BIOLOGICAL PHYSICS 



and followed by the dovetailing, inter-penetrating and 

 blending of the whole of the systemic and sympathetic, 

 nervine and non-nervine, structural elements, respectively, 

 into one organic whole, in which all are correlated and 

 co-ordinated, for systemic ends, and purposes, while struc- 

 tural and functional individuality is maintained, for local 

 ends and purposes. 



FIG. 96. SURFACE VIEW OF THE TRANSPARENT AREA OF A BLASTODERM 



OF 18 HOURS, SOMEWHAT DIAGRAMMATIC. (From Balfour.) 



pr, primitive groove, closed in front by the coalescence of the two lateral ridges ; me, 

 medullary groove, having on each side the medullary folds or ridges, A, which 

 also meet in front to enclose the groove, but diverge behind so as to enclose the 

 primitive streak ; in front the fold of the amnion is commencing. 



During this momentous period, the systemic nervature 

 inserts itself into the structural area, innervated by the 

 sympathetic nervature, while the sympathetic nervature 

 actually produces and innervates the whole of the textures 

 out of which the systemic nervature is evolved, as well as, 

 the interstitial textures of the muscular, and osseous, 

 systems, with which it is continuous in texture, and 

 function. 



The systemic nervous system (Fig. 97), including 

 brain, cord and nerves, is the crowning product of 

 developmental evolution, and, therefore, its every necessity 



