ON THE MAMMALIAN NERVOUS SYSTEM. 



501 



Averaging all the observations together, we find that the excitatory effect observed 

 in the nerve, when the uncut root was excited, amounted to 237 scale, whereas that 

 evoked by stimulating the peripheral end was 152 scale. The reduction amounts 

 roughly to about 30 per cent, of the original value, and is especially marked only in the 



Fig. 24. 



case of the posterior roots. This fact led us, at first, to believe that when a posterior 

 root was excited in its continuity, the spinal centre being of necessity aroused, there 

 must be a flow of energy from the latter down the root, and that this would provide 

 the greater effect noted. This view, however, was materially shaken by the small 

 amount of the reflex discharge obtainable from a nerve centre. We, therefore, regard 



