THE PROPERTIES 01 I \< H I'AUT OP 'Mil. REFLEX ARC 





section of the posterior roota of the spinal cord, but fail to <io so if 

 the nerve fibers are cul and allowed to degenerate, or if the stimuli are 

 blocked by applying cocaine to the skin. What actually happens is 

 evidently that the impulse Be1 up by the irritanl as it travels up the 

 afferenl fiber passes on to one of the branches above referred to, along 

 which it then proceeds to the blood vessels, which it causes to dilate 

 Thai such vasodilator impulses may l>e transmitted down the fibers 

 an afferent aerve has been confirmed by Bayliss, who found thai va 

 dilatation occurred in the hind limb when the posterior spinal roots 

 were stimulated I Bee page 23 I . 



Post, root 

 gang.- 



I -■ Diagram I n reflex of sensory nerve fiber of shin. A stimulus applied I 



the skin is transmitted by tb< i.l.< r i \ I, part . mu to the spinal co: . an>i 



part of it parsing by the collateral (C) to the arteriole i.-ii, which it causes to dilate. 



In this peripheral branching of the afferenl fibers of the skin, we 

 have therefore a sort of neuropile which, like that of certain forma 

 Celenterates see page T^-j . is capable of s,. r \ in lt as a pathway for the 

 transmission of a Bensory impulse to an effector organ without the in- 

 tervention of aerve cells. Such a reflex is known as an axon reflex, and 

 it is evident that it may occur through any fiber which gives off brand 

 one traveling to a sensory surface, the other to some effector organ, 

 occurs in the hypogastric aerves to the bladder Bee paj ~~ ; . 



THE SYNAPSIS 



At tin* poinl of ita.-t between a branch of one neuron and a nerve 



cell of the next, we have seen thai there exists structure known 

 the synapsis. Although this is described by hist . tuft-like 



