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BIOLOGY: GENERAL AND MEDICAL 



definiteness and complexity of the latter really only 

 matters of structural complexity and differentiation. 



As the phylogenetic scale is ascended the complexity of 

 the reflex circuit becomes greater and greater by the con- 

 tinuous addition of more and more nerve cells with which 



Simple reflex arc. 



Chain reflex. 



Fi2 



Complex system illustrating allied and Complex system illustrating allied and 

 antagonistic reflexes and physiolog- antagonistic reflexes with a final 



ical resolution. common path. 



Rl)> . 



Complex system illustrating the mechanism of a physiological association. 



FIG. 56. Diagrams representing the relations of neurons in five types of reflex 

 arcs: A, A. Association neurons; C, C', C", Cl, and C2, centers (adjusters); E, E', 

 E", El, and E2, effectors; FCP, final common path; R, R', R", Rl, and R2, recep- 

 tors. (Herriek, Introduction to Neurology.) 



the controllers communicate through their dendrites, un- 

 til in mammals a simple reflex act is difficult to detect, 

 A simple excitation carried to one nerve cell is transmitted 

 to so many that a very wide-spread effect may result. 



Herriek recognizes five types of reflex circuits which can 

 be understood by reference to his diagrams. 



