Fig. 27. The simplest reflex arc in the spinal cord. (After Kolliker.) 

 The afferent fiber in the posterior root (in black) gives off collaterals, which 

 end by synapses around the cells of the anterior horn (in red), the axons 

 of which form the efferent fibers of the anterior roots. (Howell's Physi- 

 ology.) 



