THE PHYSIOLOGY OF MICTUKITION 



1155 



the rectum and ends in a plexus, the hypogastric plexus, at the base of the 

 bladder. From this plexus fibres pass to the bladder wall. The pelvic 

 visceral nerves are derived from the second and third sacral nerves. They 

 make no connection with the sympathetic system, but pass directly to the 



3rd lumb. vert. 



Bladder 



Femur. _. 



Ischium 



Urethra 



Hypogastric 



plexus 

 L Sacrum 



Sciatic n. 



Sacral nerves 



FIG. 539. Nerve supply to bladder of cat. (NAWKOCKI and SKABITSCHEWSKY.) 



hypogastric plexus and are carried with branches of this plexus to the neck 

 of the bladder. The fibres do not run directly from the spinal cord to their 

 ending in the bladder wall, but make connection with cells situated peri- 

 pherally, partly in the hypogastric plexus, but chiefly in the walls of the 

 bladder itself. Both sets of fibres supply also the rectum and the colon, 

 and carry efferent impulses to the bladder. Afferent impulses from the 

 bladder travel chiefly in the pelvic visceral nerves. 



THE FILLING OF THE BLADDER 



Under normal circumstances the sphincters at the neck of the bladder are 

 in a state of tonic contraction, presenting a resistance to the emptying of 



