NERVE 93 



2. Bladder Reflex- — In connection with some of the 

 collateral ganglia apparent reflex action has been described. 

 The bladder is supplied by the hypogastric nerves which 

 come from the inferior mesenteric ganglion. The pre- 

 ganglionic fibres to this are in the splanchnic nerves. 

 When the splanchnics are stimulated the bladder contracts. 

 But if they are cut above the ganglion, stimulation of the 

 central end of one cut hypogastric will cause contraction of 

 the bladder if the other hypogastric is intact (fig. 41). 



Langley and Anderson argue that this is not a true 

 reflex, but that it is due to the fact that a nerve will conduct 

 in both directions, so that, if the hypogastric nerve is 

 stimulated, an impulse is carried up in a fibre which 



\""Ganglion or 

 \ PosteriorRoot. 



Fig. 42. — To show possible Axon Reflex in fibres of posterior root. 



bifurcates in the ganglion, one branch passing through, one 

 forming a synapse, and that, through the synapse, post- 

 ganglionic fibres in the other nerve are set in action (fig. 41). 

 They have called this an axon reflex. 



It seems just as possible that true ingoing fibres give off 

 side branches in the ganglion and produce the reflex. 



The possibility of axon reflexes occurring in visceral 

 nerves requires further investigation. 



3. Posterior Ganglion Reflex. — Bayliss has found that 

 stimulation of the peripheral end of the posterior root of a 

 spinal nerve causes vaso-dilatation in the hind leg of the dog, 

 and Bruce has shown that this may be reflexly excited by 

 applying irritants to the skin, even if the posterior root is 

 cut centrally to the ganglion. The conclusion has been drawn 



